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Frequently-Asked Gardening Questions
Q: What can you tell me about the blue lace plant? It looks like Queen Anne’s-lace, except it’s sky blue. I was told that it grows wild in northern Alabama and into Tennessee, and fields of it are just mowed down.
A: Blue laceflower (Trachymene coerulea) is listed in older references by its former name, Didiscus coeruleus. It is a member of the carrot family, Apiaceae, and has finely divided leaves on slender, branching, erect stems. The small flowers are in rounded umbels two or three inches across, held aloft on stems one to two feet high. The lacy flower does resemble that of Queen Anne’s-lace, but is pale blue or lavender. The species is a native of Australia and the islands of Southeast Asia, and our references make no mention of it being naturalized in the United States. Catalogs tout it as a cut flower. It is a sun-loving annual or biennial that does best in porous, well-drained soil of moderate fertility. In greenhouses, blue laceflowers can bloom from fall to late spring. Seeds are available from several retail mail-order companies.
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Q: I have brugmansia and datura that produced seeds after flowering. I would like to know if I need to do anything prior to planting those seeds or do I just plant them? When and how do I do this?
A: These plants are not hardy. Sow seeds at 61 degrees Fahrenheit in the Spring. All parts are highly toxic if ingested so be careful. Outdoors these plants grow in fertile, moist, but well-drained soil in full sun.
Q: I’ve always admired caladiums but never grew them until this year. One plant put up two leaves and then a strange-looking Back To Top
thing that definitely was not a leaf. It turned out to be a spathe with a fat spadix inside. How common is this, and does the spadix contain both male and female flowers?
A: It’s not very common for caladiums to form flowers, but apparently the environmental conditions in your garden were just right for them. Like the related calla lily and Jack-in-the-pulpit, the flowering structure consists of a hooded, petal-like bract called the spathe and a spike called a spadix. The tiny flowers are crowded along the spadix with the female flowers on the lower part and the male flowers above them. Following pollination the plant will form white berries.
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Q: I am looking for ideas for containers on a porch in full sun. I prefer mixed plantings of long-blooming annuals with foliage accents. I do have the AHS book on containers, but am still at a loss. Suggestions will be much appreciated.
A: There are endless possibilities of annuals that you can plant for container gardening. Marguerites are white, golden eyed daisies that continuously bloom all summer. Cockscomb (celosia) are feathery and bright colored, Diascia trail nicely, as do lobelia and nasturtiums. The gray wooly leaves of helichrysum petiolare love baking in the sun. Heliotropes have a wonderful fragrance and violet-blue flowers, and stock flowers too smell nice. Petunias , snapdragons, and geraniums, salvias, pansy, and verbena are wonderful too. For foliage accents you can plant canna, coleus and dusty miller.
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Q: A plant by the name of Flowering Maple was given to me and I have no information on it except it is a tropical plant. Anything you can tell me about it would help. How much water and light does it need? How big does it get?
A: Your plant is Abutilon. Outdoors, it requires moderately fertile, well-drained soil and full sun.
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Q: My hollyhocks have all bloomed out and look pretty bad thanks to the Japanese beetles. Should I cut them down to the ground now? Every year I shake out the dry seeds, but never get any babies.
A: Hollyhocks are biennials, and according to our sources if you have been growing them longer than 2 years, the seeds that you are shaking out are the replacement plants that come up every year. Cutting them back after the Japanese beetle attack will certainly clean up the area, but you will sacrifice your seeding.
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Q: I like to grow impatiens in the annual parts of my flower beds, but the last few years some of the plants have wilted and died after they seem to be well established. It is not due to lack of moisture. The beds have been watered when they needed it.
A: Impatiens need partial shade meaning they like quite a bit of shade and require only a few hours of sunlight. They don’t like afternoon sun and prefer morning sun. They will get scorched if they are in direct sunlight even for an hour or two. However, the New Guinea hybrid impatiens (larger flowers and elongated green or variegated leaves) will tolerate full sun if the soil is kept moist. Impatiens also need average soil and water during droughts.
There is a possibility that they may have Verticillium wilt that is caused by a fungus. The solution for this is to use clean soil or treat infested soil with heat or chemical. The other possibility is that it may have bacterial wilt and the solution for this is to remove and destroy affected plants and before replanting you need to replace the soil in which diseased plants appeared. Before doing any of these you should contact your cooperative extension for advice.
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Q:Seed packets and planting guides often say to plant when danger of frost has passed. How do I know when that is?
—S.P., South Bend, Indiana
A: In your area, April 30 is the projected date for the last killing frost, according to a map published in U.S. Department of Agriculture “Home and Garden Bulletin 202.” This date could differ as much as one to two weeks within 10 miles of your home. It is best to check with your county Extension agent or local weather bureau.
Keep in mind that this is the average date for the last frost that will kill established perennials to ground level. When installing tender plants or sowing seeds, wait a few weeks so the soil can warm to a safe temperature.
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Q: Can you supply me with the botanical or common names of those annual “poppies” (whether Papaver or not) that can be direct-seeded outdoors even under frost conditions.
A: The California poppy is called Eschscholzia californica. It is best to sow the seed in situ in the early spring or where winters are mild. They can be planted in autumn through early spring. They perform most successfully in the moderate temperatures of the Pacific Coast. They can be started indoors 2-3 weeks before the last frost but do best when planted directly outside.
Some annual varieties of the Papaver family include the P. rhoeas (corn poppy, field poppy, Flanders poppy, and the Shirley series). These can be sown indoors 6-8 weeks before the last frost, in peat pots. Best results come from seeds started in situ. In zones 3-7, sow in early spring, when soil is cool and a light frost is still possible or in late autumn. Where summers are cool, 3 spring plantings made 6 weeks apart will prolong the blooming season. In zones 8-10, sow only in autumn.
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Q: I’ve noticed that the ‘Marguerite’ and ‘Blackie’ cultivars of sweet potato vines are readily available in the trade. Are the swollen underground roots of these cultivars edible like a “normal” sweet potato? Can you propagate the sweet potato from these roots?
A: Unlike their agricultural counterparts, Ipomoea batatas ‘Marguerite’ and ‘Blackie’ are bred for ornamental properties rather than edible roots. ‘Marguerite’ is grown for its broad, heart-shaped, chartreuse foliage on trailing vines, and ‘Blackie’ is becoming a favorite in the garden for its dark purple, deeply lobed foliage that makes a great companion for plants with brightly colored flowers or foliage.
According to Janet Bohac at the USDA’s Vegetable Laboratory in Charleston, South Carolina, ‘Marguerite’ seldom produces a “usable” edible root and ‘Blackie’ almost never does. If, by chance, such a root is produced, there is no reason it could not be eaten.
Bohac adds that while it is possible to propagate these varieties from slips produced by their roots, propagation from cuttings is much easier.
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Q: The garden section of one of my magazines referred to a planting of tweedia. It looked beautiful, but I can’t find the plant listed in any of my gardening books. Can you tell me a little about it?
A: Even gardening books that talk about this plant, Tweedia caerulea, usually use its former name, Oxypetalum caeruleum. It is also called southern star and blue milkweed, since it is a member of the milkweed family. It is a native of the tropics of South America, so must be grown as an annual in the United States. Not really a vine but more of a subshrub, it has twining stems to three feet tall. Its most spectacular feature is its flower color, described as a powder blue tinged with green that makes it almost turquoise, becoming lilac as it ages.
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Q: My daughter gave me some summer-flowering allium bulbs for Christmas. Can I plant these the same way as I do my spring-flowering bulbs, and can you give me suggestions for other summer-flowering bulbs to add to my garden this spring?
A: Like most hardy bulbs, alliums are best planted in early fall, but you may get away with planting them in early spring if you can store them in a cool, dry place. Another option is to plant them now in a large container and place it outside or in an unheated garage so they will get enough chilling to bloom. Make sure the soil around them stays slightly moist but not waterlogged.
Some other hardy summer-flowering bulbs to consider include Sicilian honey garlic (Nectaroscordum siculum) and native spider lilies such as Hymenocallis caroliniana and H. liriosome, which are hardy to USDA Zone 7. “Crinum lilies would be really good for Chapel Hill,” says Nancy Goodwin, creator of Montrose gardens in Hillsborough, North Carolina. Crinums and spider lilies have an advantage over some other summer bloomers in that they don’t mind clay soils, and some even thrive with wet feet. Despite references that indicate these bulbs are hardy only in Zone 9 or 10, Goodwin has had no problem growing Crinum ‘Ellen Bosanquet’, C. ‘Milk and Wine’, or Amarcrinum memoria-corsii, a hybrid between Amaryllis belladonna and Crinum moorei. Good choices for lower-growing bulbs, according to Goodwin, are rain lilies such as Zephyranthes candida, Z. flavissima, and Habranthus robustus, which flower after rainfall throughout the summer. Old favorites include Gladiolus, Crocosmia, and, of course, many, many lilies (Lilium spp.)
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Q: Could you please advise me about the best time to divide Amaryllis Bulbs and how deep to replant them? They have been in my flowerbed for approximately four years. It seems that the only information I can find on these bulbs pertains to growing them indoors.
A: Since Amaryllis bulbs do not like to be disturbed, it is best to remove offsets each year. This will also encourage the growth of large, single bulbs. If the offsets are left attached, however, large clumps will eventually form and they will have to be divided. This should be done in autumn, and the bulbs should be replanted with neck and shoulders above the soil surface.
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Q: I’ve always admired caladiums but never grew them until this year. One plant put up two leaves and then a strange-looking thing that definitely was not a leaf. It turned out to be a spathe with a fat spadix inside. How common is this, and does the spadix contain both male and female flowers?
A: It’s not very common for caladiums to form flowers, but apparently the environmental conditions in your garden were just right for them. Like the related calla lily and Jack-in-the-pulpit, the flowering structure consists of a hooded, petal-like bract called the spathe and a spike called a spadix. The tiny flowers are crowded along the spadix with the female flowers on the lower part and the male flowers above them. Following pollination the plant will form white berries.
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Q: I have a cultivated ginger plant that is about three years old and seems to be thriving, but it has never bloomed. It sits in a chilly room in the winter, probably 50 degrees, and in the summer it goes outside where it is sunny. It is about five feet tall and looks healthy. I live in New England. How do I get it to bloom?
A: Most likely you have common ginger (Zingiber officinale), a native of tropical Asia. The aromatic, edible rhizomes of ginger are extremely versatile and widely used in Asian cuisine and medicine. This perennial herbaceous plant has thin stems and scattered, pointed leaves; it can grow up to five feet tall. Unfortunately, blooms are rarely produced on this species. According to Liz Bodin at Stokes Tropicals in Louisiana, “The flowers of Zingiber officinale are small and rare. Gingers love long periods of summer and grow best in Zone 8 or higher. North of USDA Zone 8 they do not really have a long enough growing season to produce flowers.” She suggests applying a diluted fertilizer regularly during the growing season to try to promote flower growth.
If you are interested in a flowering ginger plant, you might want to try growing Zingiber mioga—an edible ginger grown for its flowers and colorful new shoots and Z. rubens, or Z. spectabile. These and other varieties can be ordered through Stokes Tropicals at www.stokestropicals.com.
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Q: Last fall I noticed squirrels digging in my garden and now none of my spring bulbs are blooming. Did those fluffy-tailed rats eat my bulbs? If so, how can I keep them from doing the same thing this fall
A: Squirrels like to eat and gather seeds, roots, berries, buds, and bulbs, so it’s quite likely that your bulbs were stolen by your fluffy-tailed friends. There are several ways to deter squirrels from digging in your garden. One method is to sprinkle hot pepper in the hole when planting bulbs or mix a little with seeds before sowing. Screen can be inserted in the ground around the bulbs. Mothballs in mesh bags scattered throughout the garden may help keep away squirrels as well as deer and skunks. Some people use deer repellent to discourage these rodents.
Here at River Farm we have found that the dried blood usually used as fertilizer works temporarily when scattered on top of the soil. One staff member lays trimmings from rose bushes on top of containers and new plantings.
Before deciding to use lives traps, check with your local animal control department. Many jurisdictions prohibit the release of animals into unfamiliar habitats. If you do use live traps, bait them with peanut butter, corn, oats, or nuts. Do not use poison because it could be dangerous to other animals and pets who feed on dead rodents. Do not handle trapped pests because they may carry parasites that can affect humans.
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Q: I’ve noticed that the ‘Marguerite’ and ‘Blackie’ cultivars of sweet potato vines are readily available in the trade. Are the swollen underground roots of these cultivars edible like a “normal” sweet potato? Can you propagate the sweet potato from these roots?
A: Unlike their agricultural counterparts, Ipomoea batatas ‘Marguerite’ and ‘Blackie’ are bred for ornamental properties rather than edible roots. ‘Marguerite’ is grown for its broad, heart-shaped, chartreuse foliage on trailing vines, and ‘Blackie’ is becoming a favorite in the garden for its dark purple, deeply lobed foliage that makes a great companion for plants with brightly colored flowers or foliage.
According to Janet Bohac at the USDA’s Vegetable Laboratory in Charleston, South Carolina, ‘Marguerite’ seldom produces a “usable” edible root and ‘Blackie’ almost never does. If, by chance, such a root is produced, there is no reason it could not be eaten.
Bohac adds that while it is possible to propagate these varieties from slips produced by their roots, propagation from cuttings is much easier.
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Q: My tuberous begonias have been blooming non-stop in hanging baskets for at least 10 years. Now the stems have started to rot and break off. The soil doesn’t seem too wet. What am I doing wrong?
A: Your plants could be infected with a fungus that causes stem rot, a common problem with tuberous begonias that is usually associated with over-watering or planting the tubers too deep. The tubers should be covered with only half an inch of light potting soil, and the soil should be allowed to dry out a bit between waterings. Keeping the plant in a location where it receives good air circulation is helpful, and good plant hygiene is essential. Remove spent flowers before they fall into the foliage, where they can encourage fungal growth.
However, 10 years may be about as much as you can expect out of your tuberous begonias; the plants may simply be displaying the stress of old age. In this case, new tubers are the answer. Although tuberous begonias can be overwintered in their pots, it may be better to remove the tubers in autumn and put them in a sunny, airy location to “ripen.” When the stems and leaves have dried, clean the tubers, dust them with elemental sulfur, and store them in dry sand or peat moss at about 45 degrees Fahrenheit until it’s time to plant them again next spring.
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Q: What are the different types of broad beans and their botanical names? What are they used for, and where are the commonly grown?
A: One of the oldest known cultivated plants, the broad bean or fava bean (Vicia faba) is a legume related to vetch. Native to Africa and the Middle East, it is also known as Windsor bean, Scotch bean, and horse bean.
Broad beans make an excellent substitute for lima beans in cold, short-season areas where the latter cannot be grown successfully. Plant them in the spring as soon as the ground can be worked (at the same time as peas). They need the long cool springs to set their pods; warm weather—above 70 degrees Fahrenheit—inhibits flowering and pod setting. Broad beans will survive frost but not a heavy freeze. Their taste has been described as between that of a garden pea and a lima bean, with rich nutty overtones.
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Q: Are cashews true nuts? Although they’re commonly referred to that way, from a botanical point of view I don’t think they are.
A: You’re correct. In The Book of Edible Nuts, author Frederic Rosengarten Jr. points out that “few botanical terms are used more loosely than the word ‘nut.’” According to the strict botanical definition, the cashew is a seed contained within a drupe—a stone fruit whose seed is protected by a hard casing within a fleshy layer.
By comparison, the botanical definition of a nut is: “A type of fruit that consists of one, often edible, hard seed covered with a dry, woody shell that does not split open at maturity.” True nuts include chestnuts, filberts, and acorns.
The cashew fruit consists of two parts. The cylindrical upper section, which is from two to four inches long, is a fleshy, swollen portion of stem known as the cashew apple. The juice from this “fruit” is used to make candies, syrups, jams, vinegars, and even wines. The kidney-shaped “nut” is contained within a semi-hard, grayish brown shell, usually less than half as long as the apple, attached beneath the cashew apple. The one-eighth-inch-thick nutshell contains a toxic, resinous sap that is processed for use in a variety of commercial applications. The sap must be removed, traditionally by roasting, before the nuts can be harvested.
Much fascinating information about the cashew and many other edible nuts can be found in Rosengarten’s book, published in 1984.
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Q: I have two seven-year-old cherry trees in my yard that fruit abundantly each year, but when the cherries ripen, many contain small white maggots. How can I eliminate this pest without using chemical sprays, which may kill honeybees?
A: The quarter-inch-long maggot inside your cherries is probably the larvae of the cherry fruit fly, which looks much like a small housefly but has bold diagonal markings on its wings. This fly pupates in the soil beneath cherry trees, emerging in late spring to lay eggs in the fruit. After hatching, the maggots feed and penetrate to the pits, causing fruit rot. Finally, the maggots drop to the ground and bury themselves below the surface. Because cherry fruit flies leave little evidence of their egg-laying, it is difficult for the home gardener to detect their presence until it is too late.
To control the fruit fly, try trapping adults in the spring before they lay their eggs. In late May—or whenever cherry fruits begin to form in your area—hang four to eight red sticky spheres or yellow cards on the branches of each cherry tree. Hang the traps at eye level, about two to three feet from the tips of the branches. Clean off the trapped flies every few days and reapply the sticky coating if necessary.
To reduce future infestations, clean up fallen fruits under the tree daily and destroy them. For severe infestations, you may choose to try botanical insecticides such as rotenone or neem, but as with all pesticides, be sure to follow the manufacturers’ instructions for safe use. Many of these organic controls,
including the sticky traps, can be found at your local garden
center. Two mail-order sources are Gardens Alive! 5100
Schenley Place, Lawrenceburg, IN 47025; (812) 537-8651;
www.gardens–alive.com; and Planet Natural, 1612 Gold Avenue, Bozeman, MT 59715; (800) 289-6656; www.planetnatural.com.
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Q: I would like my brother to bring back some French tarragon for me when he goes to France. What are the rules for importing plants into the United States?
A: Importing plants into the United States from another country is governed by the Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of Agriculture. According to APHIS’s plant protection and quarantine import permit unit, live plants of most common culinary herbs, including French tarragon (Artemisia dracunculus), can be imported into the United States as long as they are packed in a sterile, soilless mix.
To prevent soil organisms from arriving along with your plant, all plants brought into the United States must be free of sand, soil, earth, leaf mold, and any other decayed vegetable matter. To pack the plant for transport, you may use ground peat, sphagnum, coco dust, osmunda fiber, wood shavings, sawdust, ground cork, buckwheat hulls, polymer-stabilized cellulose, or exfoliated vermiculite.
In addition, plants for import need to be clearly labeled with their scientific name and cultivar name. You will also need an invoice for the plant and may need certification by plant quarantine officials in the plant’s country of origin. Whether you will need certification by plant quarantine officials depends on which country the plant came from and on whether the plant is known for carrying specific diseases or pests. The nursery that sells you the plants may be able to give you information on this, but to be safe you may want to contact that country’s agriculture department. The best way to find out information on certification is to check with APHIS officials before leaving the United States.
For more information from APHIS on importing plants, including how to get import permits, visit their Web site at www.aphis.usda.gov/ppq/bats.
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Q: Our grafted peach tree was hit by construction equipment and is now resprouting from the base of the trunk. What can we expect to happen?
A: Grafting is normally done to give a tree a characteristic that it doesn’t naturally have—compact size, disease-resistant roots, or the ability to bear several different flowers or fruits, for instance. You may have seen something advertised as a “fruit cocktail tree,” which has peaches, plums, nectarines, and apricots all growing on the same tree; this was done by grafting.
If you are afraid you may have lost the scion—the plant that was grafted onto the rootstock—check your plant for unusual characteristics. In your case, your tree may start producing leaves of a different shape, or a different variety of peach. Modern roses, which are commonly grafted, will produce flowers that are smaller or a different color. Usually the rootstock is chosen for toughness and may not be up to your standards for ornamental or fruiting qualities. Only you can decide if the surviving tree is worth keeping.
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Q: Every year I have beautiful green grapes on my vines, but before they ripen they turn black. What can I do about it?
A: It sounds like you have the vintner’s ancient scourge, grape black rot. It usually starts with small spots on the foliage that enlarge and are surrounded by a darker brown border. Spots also appear on the fruit, but, as you noticed, not until they are about half grown. They enlarge quickly, rotting the entire grape in a few days. The diseased fruits turn black, shrivel, and dry up; they look very much like raisins and are known as mummies.
Grape black rot is caused by a fungus, Guignardia bidwellii, and is a serious problem for grape growers, since all cultivars are susceptible. Wayne Wilcox, a specialist in grape diseases at Cornell University in Ithaca, New York, explains that sanitation is of utmost importance for control. The fungus produces two types of spores: The overwintering spores survive on mummies and these are airborne, thus any infected fruit left on the ground or on the canes becomes the primary source of infection. Later, the disease is further spread through waterborne spores that develop on infected fruit. Remove all mummies from the vines and from the ground beneath. Mulching to cover any remaining overwintering spores creates a physical barrier that will help reduce infection.
Wilcox suggests that fungicides may be necessary to control the fungus, and timing is critical for their application: The first should be applied right at the start of bloom, followed by one or two more applications at two week intervals. Mancozeb and Captan are two commonly used fungicides for black rot.
If the disease has been left untreated for several years, Wilcox warns that the fungus may also be overwintering in cane lesions. Infected canes should be removed if possible, but if not, a delayed dormant spray of liquid lime sulfur—applied at the first sign of bud break—will help. “It is sort of a trade-off,” says Wilcox. “It burns the heck out of everything,” both the emerging buds and the fungus. But, it may be a necessary procedure if the canes are severely infected.
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Q: A friend wants to start a grape vine from a set of vines growing at his mother’s house. Should we start from seeds, or would it be best to take cuttings of the old vines?
A: Although grapes can be propagated from seed, this is rarely done because most grape plants are cultivars and won’t come true from seed. But you have three other options. The first option is to take hardwood cuttings. All grapes grown in the U.S., except Muscadine, can be propagated from hardwood cuttings. In the winter, take one-foot cuttings that have three buds and store them in moist sand or sawdust until early spring, when they should be planted with the top bud level with the surface of the soil. The cuttings should produce vines by the end of the first or second season.
Your other options are to take softwood cuttings or to layer a vine. Both methods work with all grapes, including Muscadine. Softwood cuttings should be taken before the stems harden in early summer and planted immediately. Layering involves taking a vine growing on the parent plant, breaking—but not severing—it at a node, and burying the node in the soil alongside the parent plant. Once roots form—usually within a year—the new plant can be separated and transplanted.
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Q: I am planning a period garden for our town’s sesquicentennial and am trying to find out what vegetables grew in a typical American garden around 1849. Where can I find this information?
A: There have been so many regional and cultural influences on gardening in America that it is difficult to define a “typical” American garden in the mid-19th century. “The Melting Plot,” a two-part article by Susan Davis Price in the March/April and May/June 1998 issues of The American Gardener provides an excellent overview of immigrant influences on American garden plants and design.
Your town’s historical society may maintain an archive of Civil War diaries and local newspaper clippings. These may provide references to the vegetables that were grown in your area.
The Thomas Jefferson Center for Historic Plants collects, preserves, and distributes plants documented to have been grown in American gardens before 1900. The center offers historic seeds for sale in its catalog. Write to Twinleaf Catalog, P.O. Box 316, Charlottesville, VA 22902, or visit its Web site at www.monticello.org/shop.
You may also want to consult The Field and Garden Vegetables of America by Fearing Burr, first issued in 1863 and reprinted in paperback by The American Botanist, Booksellers (agbook @mtco.com) in Chillicothe, Illinois, in 1998. Other worthy resources include Heirloom Vegetable Gardening by William Woys Weaver (Henry Holt and Co., 1997); Beautiful American Vegetable Gardens by Mary Tonetti Dorra (Clarkson N. Potter, 1997); and A Celebration of Heirloom Vegetables by Roger Yepsen (Artisan Books, 1998).
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Q: We have horseradish in our garden. How should I harvest and store it?
A: Hardy to USDA Zone 3, horseradish (Armoracia rusticana) is an herbaceous perennial native to eastern Europe and western Asia. It is grown for its thick taproot, which is grated to add pungency to sauces, relishes, and salads. A member of the mustard family (Brassicaceae), horseradish can spread aggressively in rich, loamy soil. You can control this tendency by harvesting it annually.
Annual harvesting also benefits flavor: Horseradish roots tend to lose their intense flavor and get stringy if left in the ground for more than one season. Harvest horseradish each fall after a few sharp frosts have stimulated the plant to begin storing starch in its roots. Dig up the entire plant and remove the foliage and any side roots. Sturdy six- to 12-inch-long side roots can be stored in moist sand or sawdust in a cool area over winter and planted the following spring.
Plant root cuttings two feet apart and four to six inches deep in fertile, well-drained soil and full sun. Set the cuttings at a slight angle in the soil, making sure the bottom end of each cutting is oriented downward. Horseradish should be included in a regular crop rotation to reduce the build-up of the soil-borne pests and diseases to which the mustard family is susceptible. Water regularly as needed during the season; the roots become woody if subjected to prolonged dry spells.
Karan Davis Cutler, author of Burpee’s Complete Vegetable and Herb Gardener: A Guide to Growing Your Garden Organically (Macmillan, 1997), recommends grating and storing in the refrigerator only as much horseradish root as you will use in a month. The ungrated portion of the root can be stored in damp sand in a cool, dark location or in a perforated plastic bag in the refrigerator for up to three months.
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Q: I recently purchased a Japanese persimmon, and a reference I consulted said it could produce parthenocarpic fruits. Does this mean it is self-pollinating?
A: Japanese persimmon (Diospyros kaki) is parthenocarpic, which means it is capable of producing mature fruits without benefit of fertilization, or sometimes even of pollination. The resulting fruits will then be seedless. If you planted your tree with other Japanese persimmons, however, cross-pollination will likely occur and the fruits will bear seeds.
The term “parthenocarpic” is derived from the Greek roots parthenos, which means “virgin,” and karpos, which means “fruit.” Notable examples of parthenocarpic fruits include navel orange, banana, and pineapple. Brian Capon, author of Botany for Gardeners, notes that not all seedless fruits are parthenocarpic. Some seedless grapes, for instance, develop after pollination and fertilization, but embryoes abort before seeds enlarge.
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Q: There are a number of pawpaw trees growing in a forested area on property I own in Indiana, but I rarely see any fruit on them. How can I get the trees to produce fruit?
A: Neal Peterson, founder of the non-profit PawPaw Foundation, says pawpaw trees are generally self-incompatible—requiring a genetically different tree for successful fertilization and fruit set to occur. In the wild, pawpaws often spread by root suckers and form groves of trees with identical genotypes. Additionally, natural pollinators of pawpaw flowers—bees, flies, and other insects—are not always dependable or available. Trees in a wooded setting are also often heavily shaded and thus less vigorous than trees in the open.
To improve fruit set, Peterson recommends thinning trees around the pawpaws to provide more light, transplanting wild pawpaws from other areas of the woods to offer genetic variability, and hand-pollinating pawpaw flowers when they bloom in early spring. But the best way to ensure the development of quality fruit, Peterson says, is to purchase grafted clones of several pawpaw cultivars and plant them in an area where they will receive full sun.
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Q: How do I germinate pecan nuts? I have nuts from a very prolific tree from Texas and would like to see if I can obtain some seedlings.
A: Pecans should be planted in early spring after cold treatment for at least three months. Recommended planting depth, according to our references, ranges from three-quarters of an inch to three inches; plant the seeds six to eight inches apart.
There are two reasons, however, that you may want to rethink the idea of growing pecans from seed. First, the minimum seed-bearing age of the plant is 10 to 20 years. Second, assuming that the tree you describe is the unimproved native pecan, Carya illinoinensis, it is unlikely to be as prolific in your home state. Although pecan trees will grow in the Northeast, they do not usually produce filled nuts. You may want to consider planting a grafted tree. Two cultivars recommended for northern growers are ‘Colby’ and ‘Peruque’.
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Q: Is there such a thing as a vegetable called a pregnant onion?
A: Pregnant onion (Allium cepa) is more commonly known as Egyptian or top onion. Its unusual name is derived from the way a dense cluster of tadpole-shaped bulblets form at the tip of the plant’s stem. These small bulbs can be harvested and eaten when the onion tops begin to wilt and dry out. Egyptian onion’s underground bulbs can become rather strong-tasting late in the season, but can be harvested in early spring as green or bunching onions. Plant Egyptian onions in fall by setting out bulblets in well-prepared soil amended with organic matter. They will tolerate a hard freeze so that plants left over from the previous season can sometimes be harvested even into winter.
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Q: Our local supermarket frequently displays vegetables labeled “malanga” and “yuca.” Could you tell me a little about them and explain how they are eaten?
A: Malanga and yuca are popular root crops in the Caribbean and South and Central America. Malanga (Xanthosoma spp.)—also known as yautia, tannia, and cocoyam—is related to, and sometimes confused with, the more familiar taro (Colocasia esculenta). There are approximately 40 species of Xanthosoma native to the American tropics. Weighing from one-half to more than two pounds, these tubers are roughly club shaped with a shaggy brown skin. The interior is creamy yellow or pink, with a crisp yet slippery texture and a flavor described as nutty or earthy. Elizabeth Schneider, author of Uncommon Fruits and Vegetables: A Commonsense Guide, writes that malanga is usually peeled and boiled in salted water for 20 to 25 minutes, then served much like a boiled potato. She lists recipes for malanga chips, pancakes, and fritters.
Yuca (pronounced YOO-kuh)—also called cassava, manioc, and tapioca—is the swollen root of an ornamental tropical shrub or small tree called cassava (Manihot esculenta). Native to Brazil, cassava is now cultivated widely throughout the Southern Hemisphere. Shaped like sweet potatoes, individual yuca roots measure two to four inches in diameter and can weigh up to three pounds. The tough, barklike brown skin is difficult to peel, but can be sliced off to reveal the hard white flesh beneath. When cooked, the flesh becomes glutinous and translucent. Rather bland on its own, yuca is used as an additive in many dishes, including soups, stews, breads, and desserts. Americans are most familiar with yuca as the thickening agent in tapioca pudding.
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Q: I used to buy a spice called star anise at the local health food store. I believe it was actually the dried seed head of the plant. What is the “real” name of the plant?
A: Star anise (Illicium verum) is a magnolialike evergreen tree native to Japan, China, and India. Its glossy brown seedpods are star shaped and have a very pronounced aniselike fragrance, hence the common name. In its native environment, the seed pods are burned like incense to scent homes, and they are chewed after meals to freshen breath. The seed pods are also used as a seasoning in Asian cooking and are often an ingredient in Chinese five-spice powder.
The tree may grow to 60 feet in height and is hardy in USDA Zones 7 to 9 and heat tolerant in AHS Zones 9 to 7. It bears small, star-shaped flowers with yellow tepals—petals and sepals that are indistinguishable—in early summer.
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Q: I’ve noticed that the ‘Marguerite’ and ‘Blackie’ cultivars of sweet potato vines are readily available in the trade. Are the swollen underground roots of these cultivars edible like a “normal” sweet potato? Can you propagate the sweet potato from these roots?
A: Unlike their agricultural counterparts, Ipomoea batatas ‘Marguerite’ and ‘Blackie’ are bred for ornamental properties rather than edible roots. ‘Marguerite’ is grown for its broad, heart-shaped, chartreuse foliage on trailing vines, and ‘Blackie’ is becoming a favorite in the garden for its dark purple, deeply lobed foliage that makes a great companion for plants with brightly colored flowers or foliage.
According to Janet Bohac at the USDA’s Vegetable Laboratory in Charleston, South Carolina, ‘Marguerite’ seldom produces a “usable” edible root and ‘Blackie’ almost never does. If, by chance, such a root is produced, there is no reason it could not be eaten.
Bohac adds that while it is possible to propagate these varieties from slips produced by their roots, propagation from cuttings is much easier.
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Q: Are cashews true nuts? Although they’re commonly referred to that way, from a botanical point of view I don’t think they are.
A: You’re correct. In The Book of Edible Nuts, author Frederic Rosengarten Jr. points out that “few botanical terms are used more loosely than the word ‘nut.’” According to the strict botanical definition, the cashew is a seed contained within a drupe—a stone fruit whose seed is protected by a hard casing within a fleshy layer.
By comparison, the botanical definition of a nut is: “A type of fruit that consists of one, often edible, hard seed covered with a dry, woody shell that does not split open at maturity.” True nuts include chestnuts, filberts, and acorns.
The cashew fruit consists of two parts. The cylindrical upper section, which is from two to four inches long, is a fleshy, swollen portion of stem known as the cashew apple. The juice from this “fruit” is used to make candies, syrups, jams, vinegars, and even wines. The kidney-shaped “nut” is contained within a semi-hard, grayish brown shell, usually less than half as long as the apple, attached beneath the cashew apple. The one-eighth-inch-thick nutshell contains a toxic, resinous sap that is processed for use in a variety of commercial applications. The sap must be removed, traditionally by roasting, before the nuts can be harvested.
Much fascinating information about the cashew and many other edible nuts can be found in Rosengarten’s book, published in 1984.
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Q: I have two seven-year-old cherry trees in my yard that fruit abundantly each year, but when the cherries ripen, many contain small white maggots. How can I eliminate this pest without using chemical sprays, which may kill honeybees?
A: The quarter-inch-long maggot inside your cherries is probably the larvae of the cherry fruit fly, which looks much like a small housefly but has bold diagonal markings on its wings. This fly pupates in the soil beneath cherry trees, emerging in late spring to lay eggs in the fruit. After hatching, the maggots feed and penetrate to the pits, causing fruit rot. Finally, the maggots drop to the ground and bury themselves below the surface. Because cherry fruit flies leave little evidence of their egg-laying, it is difficult for the home gardener to detect their presence until it is too late.
To control the fruit fly, try trapping adults in the spring before they lay their eggs. In late May—or whenever cherry fruits begin to form in your area—hang four to eight red sticky spheres or yellow cards on the branches of each cherry tree. Hang the traps at eye level, about two to three feet from the tips of the branches. Clean off the trapped flies every few days and reapply the sticky coating if necessary.
To reduce future infestations, clean up fallen fruits under the tree daily and destroy them. For severe infestations, you may choose to try botanical insecticides such as rotenone or neem, but as with all pesticides, be sure to follow the manufacturers’ instructions for safe use. Many of these organic controls,
including the sticky traps, can be found at your local garden
center.
Two mail-order sources are Gardens Alive! 5100
Schenley Place, Lawrenceburg, IN 47025; (812) 537-8651;
www.gardens–alive.com; and Planet Natural, 1612 Gold Avenue, Bozeman, MT 59715; (800) 289-6656; www.planetnatural.com.
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Q: Every year I have beautiful green grapes on my vines, but before they ripen they turn black. What can I do about it?
A: It sounds like you have the vintner’s ancient scourge, grape black rot. It usually starts with small spots on the foliage that enlarge and are surrounded by a darker brown border. Spots also appear on the fruit, but, as you noticed, not until they are about half grown. They enlarge quickly, rotting the entire grape in a few days. The diseased fruits turn black, shrivel, and dry up; they look very much like raisins and are known as mummies.
Grape black rot is caused by a fungus, Guignardia bidwellii, and is a serious problem for grape growers, since all cultivars are susceptible. Wayne Wilcox, a specialist in grape diseases at Cornell University in Ithaca, New York, explains that sanitation is of utmost importance for control. The fungus produces two types of spores: The overwintering spores survive on mummies and these are airborne, thus any infected fruit left on the ground or on the canes becomes the primary source of infection. Later, the disease is further spread through waterborne spores that develop on infected fruit. Remove all mummies from the vines and from the ground beneath. Mulching to cover any remaining overwintering spores creates a physical barrier that will help reduce infection.
Wilcox suggests that fungicides may be necessary to control the fungus, and timing is critical for their application: The first should be applied right at the start of bloom, followed by one or two more applications at two week intervals. Mancozeb and Captan are two commonly used fungicides for black rot.
If the disease has been left untreated for several years, Wilcox warns that the fungus may also be overwintering in cane lesions. Infected canes should be removed if possible, but if not, a delayed dormant spray of liquid lime sulfur—applied at the first sign of bud break—will help. “It is sort of a trade-off,” says Wilcox. “It burns the heck out of everything,” both the emerging buds and the fungus. But, it may be a necessary procedure if the canes are severely infected.
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Q: I recently purchased a Japanese persimmon, and a reference I consulted said it could produce parthenocarpic fruits. Does this mean it is self-pollinating?
A: Japanese persimmon (Diospyros kaki) is parthenocarpic, which means it is capable of producing mature fruits without benefit of fertilization, or sometimes even of pollination. The resulting fruits will then be seedless. If you planted your tree with other Japanese persimmons, however, cross-pollination will likely occur and the fruits will bear seeds.
The term “parthenocarpic” is derived from the Greek roots parthenos, which means “virgin,” and karpos, which means “fruit.” Notable examples of parthenocarpic fruits include navel orange, banana, and pineapple. Brian Capon, author of Botany for Gardeners, notes that not all seedless fruits are parthenocarpic. Some seedless grapes, for instance, develop after pollination and fertilization, but embryoes abort before seeds enlarge.
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Q: What are lingonberries? My Swedish relatives often refer to them.
—A.G., St. Paul, Minnesota
A: Lingonberry (Vaccinium vitis-idaea), also commonly known as partridgeberry or cowberry, is a low-growing, creeping evergreen shrub of European and Asian origin. An indigenous variety, V. vitis-idaea var. minus, known variously as dwarf lingonberry or mountain cranberry, is found from Labrador south to Massachusetts and west to Alaska and British Columbia. Both the species and the variety are cherished for their lustrous dark green foliage, bell-shaped white to pink summer flowers, and dark red edible berries that ripen in late summer. Lingonberries grow to about 10 inches tall, while mountain cranberries usually get no higher than four to eight inches, forming dense mats that spread by creeping rhizomes. The species is hardy to USDA Zone 5, while the variety is hardy to Zone 2. Both do well in full sun or part shade and prefer moist, acidic, rich organic soils.
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Q: There are a number of pawpaw trees growing in a forested area on property I own in Indiana, but I rarely see any fruit on them. How can I get the trees to produce fruit?
A: Neal Peterson, founder of the non-profit PawPaw Foundation, says pawpaw trees are generally self-incompatible—requiring a genetically different tree for successful fertilization and fruit set to occur. In the wild, pawpaws often spread by root suckers and form groves of trees with identical genotypes. Additionally, natural pollinators of pawpaw flowers—bees, flies, and other insects—are not always dependable or available. Trees in a wooded setting are also often heavily shaded and thus less vigorous than trees in the open.
To improve fruit set, Peterson recommends thinning trees around the pawpaws to provide more light, transplanting wild pawpaws from other areas of the woods to offer genetic variability, and hand-pollinating pawpaw flowers when they bloom in early spring. But the best way to ensure the development of quality fruit, Peterson says, is to purchase grafted clones of several pawpaw cultivars and plant them in an area where they will receive full sun.
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Q: I would like my brother to bring back some French tarragon for me when he goes to France. What are the rules for importing plants into the United States?
A: Importing plants into the United States from another country is governed by the Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of Agriculture. According to APHIS’s plant protection and quarantine import permit unit, live plants of most common culinary herbs, including French tarragon (Artemisia dracunculus), can be imported into the United States as long as they are packed in a sterile, soilless mix.
To prevent soil organisms from arriving along with your plant, all plants brought into the United States must be free of sand, soil, earth, leaf mold, and any other decayed vegetable matter. To pack the plant for transport, you may use ground peat, sphagnum, coco dust, osmunda fiber, wood shavings, sawdust, ground cork, buckwheat hulls, polymer-stabilized cellulose, or exfoliated vermiculite.
In addition, plants for import need to be clearly labeled with their scientific name and cultivar name. You will also need an invoice for the plant and may need certification by plant quarantine officials in the plant’s country of origin. Whether you will need certification by plant quarantine officials depends on which country the plant came from and on whether the plant is known for carrying specific diseases or pests. The nursery that sells you the plants may be able to give you information on this, but to be safe you may want to contact that country’s agriculture department. The best way to find out information on certification is to check with APHIS officials before leaving the United States.
For more information from APHIS on importing plants, including how to get import permits, visit their Web site at www.aphis.usda.gov/ppq/bats.
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Q: I have a cultivated ginger plant that is about three years old and seems to be thriving, but it has never bloomed. It sits in a chilly room in the winter, probably 50 degrees, and in the summer it goes outside where it is sunny. It is about five feet tall and looks healthy. I live in New England. How do I get it to bloom?
A: Most likely you have common ginger (Zingiber officinale), a native of tropical Asia. The aromatic, edible rhizomes of ginger are extremely versatile and widely used in Asian cuisine and medicine. This perennial herbaceous plant has thin stems and scattered, pointed leaves; it can grow up to five feet tall. Unfortunately, blooms are rarely produced on this species. According to Liz Bodin at Stokes Tropicals in Louisiana, “The flowers of Zingiber officinale are small and rare. Gingers love long periods of summer and grow best in Zone 8 or higher. North of USDA Zone 8 they do not really have a long enough growing season to produce flowers.” She suggests applying a diluted fertilizer regularly during the growing season to try to promote flower growth.
If you are interested in a flowering ginger plant, you might want to try growing Zingiber mioga—an edible ginger grown for its flowers and colorful new shoots and Z. rubens, or Z. spectabile. These and other varieties can be ordered through Stokes Tropicals at www.stokestropicals.com.
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Q: Our local historical society is transcribing the diaries of one of our state’s pioneer women, Myra Parsons. She and her husband farmed about 1,000 acres along the shores of Lake Huron beginning in 1876. A mother of seven children, she was a gatherer of herbs and practitioner of homeopathic medicine. She mentions a plant called mountain mist, which we have been unable to identify.
A: Myra Parsons was certainly remarkable; where did she find time to keep diaries? It appears that mountain mist is a common name for Pycnanthemum virginianum, more often called mountain mint. A member of the mint family, its leaves and stems give off a minty aroma when rubbed. It has pinkish white flowers up to one-half-inch in diameter that often form a cymelike cluster. It grows up to two feet high on stiff, erect, many-branched stems. There are actually about 20 species of Pycnanthemum native to North America, but P. virginianum is one of the most common. Found in upland woods and meadows from Maine to North Dakota and south to Georgia, it is not considered showy enough for most gardens, but can be dramatic if you encounter groupings in the wild.
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Q: I used to buy a spice called star anise at the local health food store. I believe it was actually the dried seed head of the plant. What is the “real” name of the plant?
A: Star anise (Illicium verum) is a magnolialike evergreen tree native to Japan, China, and India. Its glossy brown seedpods are star shaped and have a very pronounced aniselike fragrance, hence the common name. In its native environment, the seed pods are burned like incense to scent homes, and they are chewed after meals to freshen breath. The seed pods are also used as a seasoning in Asian cooking and are often an ingredient in Chinese five-spice powder.
The tree may grow to 60 feet in height and is hardy in USDA Zones 7 to 9 and heat tolerant in AHS Zones 9 to 7. It bears small, star-shaped flowers with yellow tepals—petals and sepals that are indistinguishable—in early summer.
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Q: I have seen a beautiful pink-flowering shrub called abutilon in several gardening magazines lately and would like to try growing it in my yard. What growing conditions does it need?
A: Abutilon is commonly called flowering maple because its foliage resembles the leaves of maple trees. You won’t be able to plant this shrub in your yard in Chicago because it needs an essentially frost-free climate to grow outdoors year-round. Abutilons are often grown as house plants and summer bedding plants, however. Look for the bushier hybrids, such as Abutilon hybridum ‘Souvenir de Bonn’ and ‘Satin Pink Belle’, which work best for indoor conditions. There are also vine-type abutilons, such as A. megapotamicum, that can be trained to grow on an indoor trellis or other type of support.
To grow indoors, they need bright direct light and fairly cool temperatures. In order for them to flower, it’s especially important that the nighttime temperature in your home is about 10 degrees cooler than during the day. During the summer, of course, you can move them outdoors.
Plant them in a well-drained fertile soil mix that includes some extra peat moss. Allow the soil to dry out slightly between waterings and feed lightly about twice a month during the growing season. A fertilizer like 15-30-15 stimulates blooming.
For readers living in USDA Zones 9 through 11, perennial flowering maples are terrific for the outdoor garden because they are low-maintenance plants that will bloom for many weeks and even months. The only care they need is an occasional pruning in late winter or early spring to keep them in good shape, and some feeding with fish emulsion, liquid seaweed, or commercial fertilizer added in the spring to stimulate growth.
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Q: Could you please advise me about the best time to divide Amaryllis Bulbs and how deep to replant them? They have been in my flowerbed for approximately four years. It seems that the only information I can find on these bulbs pertains to growing them indoors.
A: Since Amaryllis bulbs do not like to be disturbed, it is best to remove offsets each year. This will also encourage the growth of large, single bulbs. If the offsets are left attached, however, large clumps will eventually form and they will have to be divided. This should be done in autumn, and the bulbs should be replanted with neck and shoulders above the soil surface.
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Q: Can you tell me how to germinate seeds from a plant commonly referred to as bat plant (Tacca chanteri and Tacca nivea)?
A: The seeds of Tacca—a genus of 10 or so herbaceous perennials from the subtropical forests of West Africa and Southeast Asia, grown for their handsome foliage and unusual flowers—should be sown in the spring on the surface of a porous soil mix at 70 to 80 degrees Fahrenheit. Keep the seed evenly moist. Bat plants can also be propagated in spring by dividing their rhizomes; be sure each section contains a bud.
The plants require a moist, warm environment, and if grown outdoors they will need some shade. Since they are not hardy—the minimum temperature at which they will survive is 55 degrees Fahrenheit—they are often grown in a greenhouse.
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Q: I am growing several bromeliads as houseplants, but they don’t look happy. Can you help provide some information about their indoor culture?
A: The bromeliad family is made up of 2,700 species and thousands of hybrids. Most bromeliads are native to the tropics of Central and South America. Some are grown for their attractive foliage, others for their exotic flower heads. Most bromeliads flourish in bright, indirect sunlight and a humid environment where temperatures remain between 50 and 90 degrees Fahrenheit.
Proper watering is essential. Pour water into the central cup or hollow created where the leaves join the stem; the water will gradually drain into the soil. Keep the soil moist, but never allow it to get soggy. It’s also important to keep the water in the cup fresh, so flush the plant frequently to prevent stagnation and build-up of mineral salts—using distilled water will help.
Bromeliads are relatively pest-free, but occasionally they can be attacked by scale or mealy bugs. Most problems are caused by dry air, sun scorch, overwatering, or watering with hard water.
The Bromeliad Society International offers a free brochure titled “Bromeliad Culture.” To order, send a self-addressed stamped envelope to BSI at P.O. Box 12981, Gainesville, FL 32604-0981. Or visit BSI’s Web site at www.bsi.org for more information.
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Q: I have an indoor cyclamen, whose seeds I would like to germinate. It has been outside all summer and about 6-7 weeks ago it produced seeds which I collected. I have had the seeds drying in my air conditioned home since their collection. I would appreciate your recommending the best culture conditions for these seeds to germinate and grow.
A: For C. persicum, seeds are the only reliable method of producing new plants and a lot cheaper than buying quantities of tubers. Cyclamen seeds are slow to ripen. Those of summer and autumn flowering species such as C. hederifolium (syn. C neopolianum) ripen the following summer. In most cases the stems bearing the seed capsules coil down, pulling the capsules to ground level. (C. persicum does not coil.) A sticky coating, which may be pale brown, darkening with age, attracts ants, which then quickly distribute the seeds.
Cyclamen seeds are best sown fresh (gather them as they start to split.) Soak for 12-24 hours in tepid water (adding a drop of liquid soap helps water uptake and to soften seed and dissolve mucus), then drain and sow immediately. Light at this stage sends seeds into a second dormancy that is difficult to break (C. persicum hybrids can flower in as little as 8 months).
Sow large seeds in a mix of equal parts seed soil mix and sharp grit. Water, allow to drain, then seal the pots in clear plastic bags. Keep at minimum temperature of 61 degrees Fahrenheit in a lightly shaded place.
Remove bags once germination occurs. Transplant seedlings as soon as they are large enough to handle, or if the seedlings are not crowded, leave them for a year and pot the tubers singly when dormant. (This does NOT apply to C. persicum).
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Q: I have a Dieffenbachia at home and have found that it is causing a skin rash when I touch it. Is it possible that I am having an allergic reaction to my plant?
A: Commonly grown as house plants, Dieffenbachia species are actually tropical evergreen perennials in the arum family. They are distinguished by thick, clustered stems that become woody with age, draped with large, fleshy, spotted leaves. Many people are not aware that the base of the leaf stalks and stems contain a milky or yellowish sap that can cause contact dermatitis in susceptible individuals. To relieve skin irritation, wash the affected area thoroughly with soap and water; if the irritation persists, wear gloves when handling your Dieffenbachia. The plant also contains microscopic, needlelike crystals of calcium oxalate that if ingested by humans or pets can cause burning and swelling of the mouth and throat. People who experience severe reactions are sometimes unable to talk—hence one of the plant’s common names, dumb cane. Before bringing any plant into a home that includes small children or pets, be sure to find out if it is potentially toxic.
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Q: A plant by the name of Flowering Maple was given to me and I have no information on it except it is a tropical plant. Anything you can tell me about it would help. How much water and light does it need? How big does it get?
A: Your plant is Abutilon. Outdoors, it requires moderately fertile, well-drained soil and full sun.
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Q: My office-grown gardenia won’t flower. What can I do?
A: Now often listed as G. augusta ‘Fortuniana’ or even as G. fortunei, Gardenia jasminoides var. fortuniana and its cultivars are chiefly greenhouse-grown for the floral trade and are often not very rewarding when grown in the home or office. For any success you need to follow the practices of commercial growers. In winter, the plant should be kept at 45 to 50 degrees F. in indirect sun with fairly dry soil to discourage growth. In spring, prune the plant lightly, move it to a warmer and brighter location, and resume watering. During the summer, feed it regularly with fertilizer for acid-loving plants or with fish emulsion. Ensure that your gardenia is exposed to moist air by placing the pot on a tray containing pebbles and water. To develop flower buds, gardenias require at least a half-day of sun and nights cooler than 70 degrees. Any variation from these conditions is likely to result in bud drop. Therefore, the typical office environment is not conducive to a flowering gardenia.
A new cultivar developed at the Hampton Roads Experiment Station in Virginia Beach, Virginia, should make it possible to grow gardenias outdoors a bit farther north. A mature plant is said to produce up to 50 flowers from late summer into November. But while a cold hardiness rating of Zone 7 makes ‘Chuck Hayes’ a full zone hardier than other gardenias on the market, it would still need a protected situation where you are in Zone 6.
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Q: How do I propagate a gardenia using cuttings from a large gardenia bush?
A: In order to propagate the gardenia, use greenwood and semi-ripe cuttings taken as nodal stem-tip cuttings in late spring or early summer. Root one cutting per cell tray or pot. They tend to root in six to eight weeks and should be kept in humid conditions with temperatures between 68 and 77 degrees. They should flower in 12-18 months.
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Q: I have a cultivated ginger plant that is about three years old and seems to be thriving, but it has never bloomed. It sits in a chilly room in the winter, probably 50 degrees, and in the summer it goes outside where it is sunny. It is about five feet tall and looks healthy. I live in New England. How do I get it to bloom?
A: Most likely you have common ginger (Zingiber officinale), a native of tropical Asia. The aromatic, edible rhizomes of ginger are extremely versatile and widely used in Asian cuisine and medicine. This perennial herbaceous plant has thin stems and scattered, pointed leaves; it can grow up to five feet tall. Unfortunately, blooms are rarely produced on this species. According to Liz Bodin at Stokes Tropicals in Louisiana, “The flowers of Zingiber officinale are small and rare. Gingers love long periods of summer and grow best in Zone 8 or higher. North of USDA Zone 8 they do not really have a long enough growing season to produce flowers.” She suggests applying a diluted fertilizer regularly during the growing season to try to promote flower growth.
If you are interested in a flowering ginger plant, you might want to try growing Zingiber mioga—an edible ginger grown for its flowers and colorful new shoots and Z. rubens, or Z. spectabile. These and other varieties can be ordered through Stokes Tropicals at www.stokestropicals.com.
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Q: I’ve moved a big hibiscus that was outdoors all summer into our south bay window. It’s still putting out blossoms, but the leaves are dropping.
A: Don’t worry about the leaf drop. It’s natural for a hibiscus to drop leaves when it is brought into dry indoor air. Mist it often to help it adjust. It will overwinter well as long as it isn’t over-watered. This may be happening if the foliage turns from strong green to a ghostly green. If that occurs, take it out of the pot and let the root ball dry for a day or two before you put it back. Fertilize with a dilute, balanced mix once a month until the days begin to lengthen and new growth begins.
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Q: My wife loves house plants (I do the outside gardening) but seems to lack a green thumb when it comes to maintaining them. I think she kills them with kindness because no matter what the window’s light exposure and no matter how much water they receive, the plants become wilted. Do you have any suggestions for house plants for windowsill gardeners like my wife?
A: While it’s difficult to diagnose causes without seeing the actual plants, I suspect from the way you word your question that your house plants are being killed with too much of a good thing, namely water. Most plants can’t tolerate wet feet, yet many indoor gardeners admit they water daily if not twice a day. Overwatering deprives most plants of needed oxygen and makes them highly susceptible to root rot. The first symptom is often a wilted appearance, which is misinterpreted as a cry for water.
The urge to water plants constantly can be overcome. But if this act of fussing over plants is important to your wife’s enjoyment of them, there are a few house plants that do well in wet soil.
A number of experts suggest the calla lily (Zantedeschia spp.), whose pots can be left standing in saucers of water when the plants are in active growth, according to Elvin McDonald, author of The New Houseplant. McDonald also suggests two other members of the arum family: Acorus gramineus, a water garden plant with iris-like leaves, and Aglaonema modestum, a plain-leaved species of Chinese evergreen that can be grown in water. You might also try Cyperus, which are sedges that like to be standing in water while in active growth and wet at other times. Best known is probably C. papyrus, the Egyptian paper plant.
McDonald recommends changing your soil mix to something more friable, perhaps adding perlite so that there is more space for roots to get oxygen and for excess moisture to evaporate efficiently. Use unglazed clay pots—glazed or plastic pots hold in moisture—and avoid growing small plants in big pots, another situation that can lead to overwatering.
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Q: I’m looking for a house plant that doesn’t need sunlight but gives off lots of fresh oxygen. What do you recommend?
A: All plants give off plenty of oxygen, and some help to remove pollutants from the air. While no plant will grow without any light, there are many that can be grown under fluorescent lights. Unfortunately, few flowering plants will grow or thrive under standard artificial lighting, so unless you purchase and install professional-quality grow lights, you’ll have to stick to foliage plants. Some plants that do well in low-light situations include: spider plant (Chlorophytum spp.), cast-iron plant (Aspidistra elatior), golden pothos (Epipremnum aureum), kangaroo vine (Cissus antarctica), grape ivy vine (Cissus rhombifolia), spotted evergreen plant (Aglaonema costatum), Chinese evergreen (Aglaonema commutatum), and snake plant (Sansevieria spp.). Many of these common indoor house plants can be purchased at your local garden center or greenhouse.
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Q: How do I take care of a Moses-in-the-cradle plant?
A: Moses-in-the-cradle (Tradescantia spathacea; formerly Rhoeo spathacea), also called boat lily and numerous other common names, is a member of the spiderwort family. It is prized for its dark metallic green leaves that have glossy purple undersides. Small white flowers are borne within purple, boat-shaped bracts (the cradle) that are formed in leaf axils. Indoor Plants, by George B. Briggs and Clyde L. Calvin, suggests that the plants need full sun and moderate humidity, temperature, and water. The plant does not require pruning but should be fertilized four to five times per year from April to August.
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Q: I purchased, by mail-order from Ireland, a shamrock plant (along with a piece of Irish turf). How do I take care of it as a house plant?
—M.L., Buffalo, New York
A: Although the shamrock was first used as the Irish national emblem in 1681, no one plant has unquestionably been identified as the original symbol of the Christian Trinity and good luck. In 1893, Irish botanist Nathaniel Colgan asked residents of all counties of Ireland to send him specimens of “true shamrock.” Among the responses received from 26 counties were three clover species and a medic: small hop clover (Trifolium procumbens, also sold as T. dubium), white clover (T. repens), red clover (T. pratense), and the two-spotted medic (Medicago arabica). More recently, wood sorrel (Oxalis acetosella) has also been suggested for the honor. But the plant with three leaflets supposedly used by Saint Patrick to illustrate the concept of the Trinity—and presumed to be the “true shamrock”—was found on the rocky, exposed landscape of the Irish Hill of Tara. Wood sorrel, however grows only in cool, heavily shaded woodland. Red clover has been ruled an unlikely candidate because it is more delicate than white and small hop clovers. Because white clover may not be native to Ireland, the distinction of being the “true shamrock” may fall to the yellow-flowered small hop clover, which readily colonizes poor, stony ground.
Clovers need long exposure to full sun and should be grown in porous, well-drained soil. They should be kept evenly moist and fed every three to four weeks. Wood sorrel also needs a light porous soil. These rhizomatous, white-flowered plants do well in an eastern or southern exposure. Keep the soil evenly moist and feed the plant every two weeks during the growing season, but cut down on watering and stop feeding to provide a period of dormancy after flowering
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Q: How do you grow strelitzias indoors?
A: The most commonly grown strelitzia is Strelitzia reginae, commonly called bird-of-paradise. It produces brilliant, birdlike orange and purple flowers on top of long stalks of glossy greenish-blue foliage. These subtropical plants need a rich, well-drained soil containing a lot of organic matter. Place them in a brightly lit spot with temperatures of about 68 to 75 degrees during the day and night temperatures about 10 degrees cooler. During the growing season, allow the soil to dry out slightly and then water them well. Feed them with a dilute liquid fertilizer every two weeks. The plants like their foliage misted daily and year-round humidity levels of about 35 percent.
In the winter, the plants need a resting period. Keep them at about 55 degrees, decrease watering, and stop fertilizing.
Plants need to be potbound before they will flower, so don’t transplant them to a larger pot until the roots have filled up more than three-quarters of the soil area. Plants grown from seed take seven to eight years to flower. Those propagated by division take about four years.
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Q: How do you grow strelitzias indoors?
A: The most commonly grown strelitzia is Strelitzia reginae, commonly called bird-of-paradise. It produces brilliant, birdlike orange and purple flowers on top of long stalks of glossy greenish-blue foliage. These subtropical plants need a rich, well-drained soil containing a lot of organic matter. Place them in a brightly lit spot with temperatures of about 68 to 75 degrees during the day and night temperatures about 10 degrees cooler. During the growing season, allow the soil to dry out slightly and then water them well. Feed them with a dilute liquid fertilizer every two weeks. The plants like their foliage misted daily and year-round humidity levels of about 35 percent.
In the winter, the plants need a resting period. Keep them at about 55 degrees, decrease watering, and stop fertilizing.
Plants need to be potbound before they will flower, so don’t transplant them to a larger pot until the roots have filled up more than three-quarters of the soil area. Plants grown from seed take seven to eight years to flower. Those propagated by division take about four years.
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Q: How do I take care of a Moses-in-the-cradle plant?
P.C., Peoria, Illinois
A: Moses-in-the-cradle (Tradescantia spathacea; formerly Rhoeo spathacea), also called boat lily and numerous other common names, is a member of the spiderwort family. It is prized for its dark metallic green leaves that have glossy purple undersides. Small white flowers are borne within purple, boat-shaped bracts (the cradle) that are formed in leaf axils. Indoor Plants, by George B. Briggs and Clyde L. Calvin, suggests that the plants need full sun and moderate humidity, temperature, and water. The plant does not require pruning but should be fertilized four to five times per year from April to August.
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Q: My tuberous begonias have been blooming non-stop in hanging baskets for at least 10 years. Now the stems have started to rot and break off. The soil doesn’t seem too wet. What am I doing wrong?
A: Your plants could be infected with a fungus that causes stem rot, a common problem with tuberous begonias that is usually associated with over-watering or planting the tubers too deep. The tubers should be covered with only half an inch of light potting soil, and the soil should be allowed to dry out a bit between waterings. Keeping the plant in a location where it receives good air circulation is helpful, and good plant hygiene is essential. Remove spent flowers before they fall into the foliage, where they can encourage fungal growth.
However, 10 years may be about as much as you can expect out of your tuberous begonias; the plants may simply be displaying the stress of old age. In this case, new tubers are the answer. Although tuberous begonias can be overwintered in their pots, it may be better to remove the tubers in autumn and put them in a sunny, airy location to “ripen.” When the stems and leaves have dried, clean the tubers, dust them with elemental sulfur, and store them in dry sand or peat moss at about 45 degrees Fahrenheit until it’s time to plant them again next spring.
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Q: I have two seven-year-old cherry trees in my yard that fruit abundantly each year, but when the cherries ripen, many contain small white maggots. How can I eliminate this pest without using chemical sprays, which may kill honeybees?
A: The quarter-inch-long maggot inside your cherries is probably the larvae of the cherry fruit fly, which looks much like a small housefly but has bold diagonal markings on its wings. This fly pupates in the soil beneath cherry trees, emerging in late spring to lay eggs in the fruit. After hatching, the maggots feed and penetrate to the pits, causing fruit rot. Finally, the maggots drop to the ground and bury themselves below the surface. Because cherry fruit flies leave little evidence of their egg-laying, it is difficult for the home gardener to detect their presence until it is too late.
To control the fruit fly, try trapping adults in the spring before they lay their eggs. In late May—or whenever cherry fruits begin to form in your area—hang four to eight red sticky spheres or yellow cards on the branches of each cherry tree. Hang the traps at eye level, about two to three feet from the tips of the branches. Clean off the trapped flies every few days and reapply the sticky coating if necessary.
To reduce future infestations, clean up fallen fruits under the tree daily and destroy them. For severe infestations, you may choose to try botanical insecticides such as rotenone or neem, but as with all pesticides, be sure to follow the manufacturers’ instructions for safe use. Many of these organic controls,
including the sticky traps, can be found at your local garden
center. Two mail-order sources are Gardens Alive! 5100
Schenley Place, Lawrenceburg, IN 47025; (812) 537-8651;
www.gardens–alive.com; and Planet Natural, 1612 Gold Avenue, Bozeman, MT 59715; (800) 289-6656; www.planetnatural.com.
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Q: Earwigs seem to be eating everything in my garden. Are there any synthetic or natural controls?
A: Earwigs are omnivorous—they eat plants, other insects, and decaying organic matter—but the damage they cause to garden plants is usually negligible. In fact, they are predators and often help control populations of far more destructive plant feeders such as aphids, nematodes, and mites. Night-feeding earwigs are sometimes blamed for injury that other pests have caused, because they like to hide in damaged plant tissues during the day. There’s no reason to control earwigs unless you are sure they are responsible for unacceptable plant damage. In that case, you can keep them in check with insecticidal soap, which is available in most garden centers and hardware stores.
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Q: What causes fasciation? I have seen fasciated willows, but had never seen a fasciated peony until last year. In recent years my peonies have also been attacked by leaf black spot and had fewer blooms. Could this condition have caused the fasciation, or could an herbicide I used nearby have caused the problem?
A: Fasciation is a distortion of plant tissue that can be caused by mechanical or chemical injury, or by bacterial or fungal infection. Plant cells multiply abnormally, resulting in flattened or sometimes spirally curved shoots. It may appear as if several stems are fused. Among the plants commonly affected by fasciation are sweet peas, chrysanthemums, tulips, marigolds, and willows.
The inadvertent application of an herbicide could have caused the fasciation of your peonies, but if that were the case you’re lucky to have escaped with only minor damage. Herbicides should not be used where there is any chance of drift or splashing onto ornamental or vegetable crops.
Black spot is a fungal disease most commonly seen on roses. More likely your peonies are afflicted with a similar ailment variously called leaf blotch, measles, or red stem spot. This disease usually first manifests itself as dark purple spots on the surfaces of upper leaves.
Fungal diseases can usually be controlled by immediate removal of diseased leaves, followed by removal of all leaves and stems in late fall. Plants that are severely infected every year may require an application of lime sulfur spray early in the growing season. Recent research indicates that dousing plants with dilute compost tea may help prevent some fungal diseases.
Fewer blooms on your peonies could be the result of chemical stress or disease, or merely an indication that they need to be dug up and divided in late summer. Always leave two to three eyes (nascent shoots) and at least one eight-inch section of root per division. Plant divisions so that the uppermost eyes are no more than two inches below ground level.
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Q: During the last growing season I think I identified fire blight on my cotoneasters and spireas. Branches are turning brown and drying up at random spots. All the books I’ve consulted recommend streptomycin. What is this and will it do the job?
A: Fire blight is a serious disease caused by the bacterium Erwinia amylovora, which afflicts members of the rose family (Rosaceae), including pears, apples, and ornamentals such as cotoneasters and spireas. Scott Aker, integrated pest management specialist at the U. S. National Arboretum in Washington, D.C., recommends the following measures to protect your plants from the disease’s spread. Carefully inspect all branches for holdover cankers—darkened irregular collars or ridges on the bark—that serve as a reservoir for resting fire blight bacteria. Cut back affected branches well below the canker, at least six to 12 inches into healthy tissue; dispose of pruning debris with household garbage. Make sure to dip pruners into a mild bleach solution (one part bleach to 10 parts water) between plants and after completing the job to prevent cross-contamination.
Streptomycin, an antibiotic, is no longer recommended as a control because the fire blight bacterium has developed a resistance to it. Spray instead with Bordeaux mix—a blend of copper sulfate and hydrated lime—when plants are dormant, just before they leaf out in the spring. Follow manufacturers directions for spraying precautions.
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Q: Every year I have beautiful green grapes on my vines, but before they ripen they turn black. What can I do about it?
A: It sounds like you have the vintner’s ancient scourge, grape black rot. It usually starts with small spots on the foliage that enlarge and are surrounded by a darker brown border. Spots also appear on the fruit, but, as you noticed, not until they are about half grown. They enlarge quickly, rotting the entire grape in a few days. The diseased fruits turn black, shrivel, and dry up; they look very much like raisins and are known as mummies.
Grape black rot is caused by a fungus, Guignardia bidwellii, and is a serious problem for grape growers, since all cultivars are susceptible. Wayne Wilcox, a specialist in grape diseases at Cornell University in Ithaca, New York, explains that sanitation is of utmost importance for control. The fungus produces two types of spores: The overwintering spores survive on mummies and these are airborne, thus any infected fruit left on the ground or on the canes becomes the primary source of infection. Later, the disease is further spread through waterborne spores that develop on infected fruit. Remove all mummies from the vines and from the ground beneath. Mulching to cover any remaining overwintering spores creates a physical barrier that will help reduce infection.
Wilcox suggests that fungicides may be necessary to control the fungus, and timing is critical for their application: The first should be applied right at the start of bloom, followed by one or two more applications at two week intervals. Mancozeb and Captan are two commonly used fungicides for black rot.
If the disease has been left untreated for several years, Wilcox warns that the fungus may also be overwintering in cane lesions. Infected canes should be removed if possible, but if not, a delayed dormant spray of liquid lime sulfur—applied at the first sign of bud break—will help. “It is sort of a trade-off,” says Wilcox. “It burns the heck out of everything,” both the emerging buds and the fungus. But, it may be a necessary procedure if the canes are severely infected.
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Q: Late last summer, despite ample water, the leaves on several limbs of my Japanese maple suddenly began wilting. Can I save the tree?
A: What you describe is a typical symptom of Verticillium wilt, a soil-borne fungal disease that affects the vascular systems of Japanese, Norway, silver, and sugar maples, as well as many other plants. Leaves will often turn yellow or brown and entire branches will die. In Diseases and Pests of Ornamental Plants, author Pascal P. Pirone states that in the early stages of the disease wilt symptoms are usually confined to single branches or to one side of the tree. Small plants or trees may die within a single season, but larger, mature trees may live for many years, or even recover from the disease under optimal conditions. Trees showing widespread and severe infection are unlikely to be saved. In cases where only a few branches are affected, the tree may be helped by regular watering and the application of a slow-release fertilizer around the base of the tree early in the growing season. Regular applications of fertilizer stimulate rapid growth and may result in the formation of a thick layer of sapwood that seals off the infected tissue. Diseased branches should be cut off well below the affected section and destroyed. Plants that are susceptible to Verticillium wilt should not be planted in soils known to be infected with the fungal disease.
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Q: Last fall I noticed squirrels digging in my garden and now none of my spring bulbs are blooming. Did those fluffy-tailed rats eat my bulbs? If so, how can I keep them from doing the same thing this fall
A: Squirrels like to eat and gather seeds, roots, berries, buds, and bulbs, so it’s quite likely that your bulbs were stolen by your fluffy-tailed friends. There are several ways to deter squirrels from digging in your garden. One method is to sprinkle hot pepper in the hole when planting bulbs or mix a little with seeds before sowing. Screen can be inserted in the ground around the bulbs. Mothballs in mesh bags scattered throughout the garden may help keep away squirrels as well as deer and skunks. Some people use deer repellent to discourage these rodents.
Here at River Farm we have found that the dried blood usually used as fertilizer works temporarily when scattered on top of the soil. One staff member lays trimmings from rose bushes on top of containers and new plantings.
Before deciding to use lives traps, check with your local animal control department. Many jurisdictions prohibit the release of animals into unfamiliar habitats. If you do use live traps, bait them with peanut butter, corn, oats, or nuts. Do not use poison because it could be dangerous to other animals and pets who feed on dead rodents. Do not handle trapped pests because they may carry parasites that can affect humans.
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Q: My tuberous begonias have been blooming non-stop in hanging baskets for at least 10 years. Now the stems have started to rot and break off. The soil doesn’t seem too wet. What am I doing wrong?
A: Your plants could be infected with a fungus that causes stem rot, a common problem with tuberous begonias that is usually associated with over-watering or planting the tubers too deep. The tubers should be covered with only half an inch of light potting soil, and the soil should be allowed to dry out a bit between waterings. Keeping the plant in a location where it receives good air circulation is helpful, and good plant hygiene is essential. Remove spent flowers before they fall into the foliage, where they can encourage fungal growth.
However, 10 years may be about as much as you can expect out of your tuberous begonias; the plants may simply be displaying the stress of old age. In this case, new tubers are the answer. Although tuberous begonias can be overwintered in their pots, it may be better to remove the tubers in autumn and put them in a sunny, airy location to “ripen.” When the stems and leaves have dried, clean the tubers, dust them with elemental sulfur, and store them in dry sand or peat moss at about 45 degrees Fahrenheit until it’s time to plant them again next spring.
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Q: Two more of my most promising new shrubs have been chewed off just below the soil line by voles. I can see the tell-tale marks from their nasty little teeth! I have tried traps, Ramik pellets, and castor oil-based repellent drenches—with only moderate success. I have some hardware cloth to make protective “root cages” for replacement plantings, but I need suggestions on the best way to make them.
A: Young trees and shrubs can be protected from voles by installing cylindrical tree guards made of quarter-inch wire mesh. The guards should be taller than the average snow depth and extend three inches into the soil. The diameter of the wire mesh cylinder should be large enough to allow for five years of growth.
Keep organic mulches shallow—no deeper than one inch—because thick layers of organic mulch provide an ideal habitat for voles. Mulching with pebbles or crushed stone will create a less inviting habitat to voles; they will either avoid the area or be more easily spotted by predators.
Encouraging predators is an effective way of keeping rodent populations under control. Hawks, owls, crows, black snakes, and king snakes feed on voles.
Try placing ordinary mouse traps, baited with peanut butter or a small piece of apple peel, in or near the open end of the tunnel. A cardboard box placed over the trap and the end of the tunnel will reduce the likelihood of other animals being trapped. The use of poison baits is not recommended because of the risks to children and non-target animals. Long-term management of vole populations should be based on habitat reduction and predator encouragement rather than reliance on chemical controls.
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Q: My water garden has been taken over by algae. Is it true that water hyacinth will kill it?
A: Water hyacinth (Eichhornia crassipes) can slow the growth of algae by absorbing excess water nutrients. Research has also shown that water hyacinths can clear polluted water by filtering out potentially hazardous chemicals.
It is illegal to transport water hyacinth across state lines, however, because it is a prolific grower that has clogged waterways in the South. Although this should not be a problem in the North, since the plant is killed by temperatures under 35 degrees, you may find it ultimately more rewarding to use what water garden expert Charles Thomas calls “nature’s way of dealing with excess nutrients in water”—a combination of attractive submerged plants and scavengers. Or consider buying more benign plants, such as water lilies or floating hearts (Nymphoides spp.), to cover about 60 percent of your pond’s surface.
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Q: I am trying to control a wireworm problem, but I don’t want to use chemicals. Do you have any information on control by organic means?
A: Wireworms are the larvae of snapping or click beetles (Agriotes spp.). The yellow to golden brown grubs are one to two inches long with shiny, leathery skin and six legs near the head. They live in the soil and feed on roots, bulbs, and crowns of plants and can damage seedlings. The Complete Manual of Organic Gardening, edited by Basil Caplan, indicates that egg-laying click beetles are especially attracted to weedy sites or pasture. Wireworms are most often a problem when such ground is newly cleared. Consistent weed control will help diminish the problem. Cultivate around plants and between crops to expose the grubs to birds and other predators. Or, prior to planting time, set a food trap by burying half a potato spiked on a stick. Check the potato at regular intervals and remove and kill any wireworms.
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Q: I live in coastal North Carolina, just above Wilmington. Are there any agaves that are hardy this far north?
A: Plant Delights Nursery in Raleigh, North Carolina, offers several agaves including a couple—Agave parryi subsp. parryi and A. parryi subsp. huachucensis—described as hardy to Zones 5 and 6, respectively. Nursery owner Tony Avent says that in his experience agaves don’t mind low temperatures as much as they mind cold combined with wet weather and poor drainage. For best results, Avent recommends planting agaves early in the growing season in an area that gets full sun, has well-aerated soil, and is protected from winter winds. The drainage of the planting site can be improved by building a raised bed and amending soil with gravel or sharp sand. For a catalog, send 10 first-class stamps or a box of chocolates—no kidding—to Plant Delights Nursery, 9241 Sauls Road, Raleigh, NC 27603. The catalog is also available online at www.plantdel.com.
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Q: Can you tell me how to germinate seeds from a plant commonly referred to as bat plant (Tacca chanteri and Tacca nivea)?
A: The seeds of Tacca—a genus of 10 or so herbaceous perennials from the subtropical forests of West Africa and Southeast Asia, grown for their handsome foliage and unusual flowers—should be sown in the spring on the surface of a porous soil mix at 70 to 80 degrees Fahrenheit. Keep the seed evenly moist. Bat plants can also be propagated in spring by dividing their rhizomes; be sure each section contains a bud.
The plants require a moist, warm environment, and if grown outdoors they will need some shade. Since they are not hardy—the minimum temperature at which they will survive is 55 degrees Fahrenheit—they are often grown in a greenhouse.
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Q: I recently moved to Alabama. In the back area of our new lot I found a century plant that is seven to eight feet high and 10 to 12 feet wide. Is this size unusual? Its lower leaves are dried and shriveled—can I remove them? Would it be safe to remove surrounding vegetation?
A: There are about 200 species of century plant (Agave spp.), most of which are monocarpic—they die after flowering—but some are perennial. The monocarpic varieties usually bloom after 10 to 12 years—not a century, but a long time to wait for a flower. Some are very large, with the flower stalk reaching 20 feet or more, but some grow no higher than two feet.
Of the 50 or so varieties grown in the United States, most are native to the southwestern states and Mexico. It sounds like you may have Agave americana, sometimes called American aloe, the crown of which can reach six to 10 feet, with individual leaves up to six feet long. Because it is monocarpic, it probably won’t live very much longer. It will, however, produce a spectacular bloom when its time comes.
Pruning the dried leaves is advisable to improve air circulation and reduce the chance of disease. It is also safe to remove any other vegetation around the plant, but do this in stages to prevent a sudden change of exposure to wind and sun. Spread a two- to three-inch layer of stones or chunky bark mulch under the plant to suppress weeds. Agaves tolerate poor soils and drought conditions, so don’t fertilize or water. This is the quintessential low-maintenance plant in its native or an adapted habitat. Just sit back and wait for the show.
A useful and authoritative new reference on agaves is Agaves, Yuccas and Related Plants: A Gardener’s Guide by Mary and Gary Irish, published in 2000 by Timber Press.
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Q: What causes fasciation? I have seen fasciated willows, but had never seen a fasciated peony until last year. In recent years my peonies have also been attacked by leaf black spot and had fewer blooms. Could this condition have caused the fasciation, or could an herbicide I used nearby have caused the problem?
A: Fasciation is a distortion of plant tissue that can be caused by mechanical or chemical injury, or by bacterial or fungal infection. Plant cells multiply abnormally, resulting in flattened or sometimes spirally curved shoots. It may appear as if several stems are fused. Among the plants commonly affected by fasciation are sweet peas, chrysanthemums, tulips, marigolds, and willows.
The inadvertent application of an herbicide could have caused the fasciation of your peonies, but if that were the case you’re lucky to have escaped with only minor damage. Herbicides should not be used where there is any chance of drift or splashing onto ornamental or vegetable crops.
Black spot is a fungal disease most commonly seen on roses. More likely your peonies are afflicted with a similar ailment variously called leaf blotch, measles, or red stem spot. This disease usually first manifests itself as dark purple spots on the surfaces of upper leaves.
Fungal diseases can usually be controlled by immediate removal of diseased leaves, followed by removal of all leaves and stems in late fall. Plants that are severely infected every year may require an application of lime sulfur spray early in the growing season. Recent research indicates that dousing plants with dilute compost tea may help prevent some fungal diseases.
Fewer blooms on your peonies could be the result of chemical stress or disease, or merely an indication that they need to be dug up and divided in late summer. Always leave two to three eyes (nascent shoots) and at least one eight-inch section of root per division. Plant divisions so that the uppermost eyes are no more than two inches below ground level.
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Q: Could you give me tips on germinating some native seeds: Ruellia humilis (Wild Petunia), Tiarella cordifolia v. collina (Foam Flower), Panicum virgatum (Switch Grass)?
A: Ruellia can be sown indoors 8-10 weeks before planting out. Just cover it. Seeds germinate in 30-60 days and require temps of 65-75 degrees. Seedlings should be planted outside only when the temperatures remain above 60 degrees. Plant seedlings 18-24 inchees apart in part to full shade. Seeds can be planted outside in Spring.
Tiarella (Foam Flower) germinates in 14-90 days. For autumn sowing-sow seeds in flats, sink these to the rim outdoors against a north facing wall, and cover with glass. Moisten soil occasionally, if necessary. Bring indoors in spring to 50 degrees and transplant to the garden after the last spring frost. Spring sowing—sow seeds in moistened medium, place in a plastic bag and refrigerate. After 2-3 weeks, sink containers in the grown in a shady location, covering with glass. Remove glass when seedlings sprout. Transplant seedlings to the garden in autumn.
Panicum (switch grass) should be sown outdoors only after last frost at about 1/8 inch depth. They will germinate in about 21 days and require temperatures of 65-75 degrees. Purchased plants may be set out in spring or autumn.
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Q: I’m writing an article on Christmas plants and can find no information on the meaning of the name “hellebore.” Can you help me?
A: “Hellebore” is from the Greek words “helein,” meaning to injure, and “bora,” meaning food. These words refer to the bitter roots and leaves, which are poisonous when ingested. Even contact with bruised leaves can cause severe dermatitis in susceptible individuals. You’re probably writing about Helleborus niger, the Christmas rose or black hellebore, an old and much-beloved garden standby. This winter bloomer can be brought indoors to enjoy if the plant is dug carefully in early fall, and can also be used as a cut flower if the stems are slit.
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Q: I have Joe-Pye weed in my garden that needs to be cut back. Although the roots are fairly close to the surface, they are thick and tough and I am having trouble getting them out. Do you have any suggestions?
A: Joe-Pye weed is the common name for several plants in the genus Eupatorium. The most commonly grown species are common Joe-Pye weed (E. purpureum), hollow Joe-Pye weed (E. fistulosum), and spotted Joe-Pye weed (E. maculatum).
A member of the aster family (Asteraceae), this bold North American native perennial grows five to 10 feet tall—depending on species or cultivar—and up to five feet in diameter. Joe-Pye weed makes an architectural statement in the garden, and its clusters of purple flowers attract butterflies.
Joe-Pye weed can be dug and divided annually, preferably in the fall, to prevent its root system from spreading too far from the parent plant or plants. There is, unfortunately, no real short cut to the digging process. Digging should become easier if you retain one main stem and dig and divide the plant every year.
If digging is not feasible, prune back unwanted new growth as soon as it appears in spring, or add a weed-blocking landscape fabric—camouflaged by mulch—around the plant’s main stem.
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Q: Our local historical society is transcribing the diaries of one of our state’s pioneer women, Myra Parsons. She and her husband farmed about 1,000 acres along the shores of Lake Huron beginning in 1876. A mother of seven children, she was a gatherer of herbs and practitioner of homeopathic medicine. She mentions a plant called mountain mist, which we have been unable to identify.
A: Myra Parsons was certainly remarkable; where did she find time to keep diaries? It appears that mountain mist is a common name for Pycnanthemum virginianum, more often called mountain mint. A member of the mint family, its leaves and stems give off a minty aroma when rubbed. It has pinkish white flowers up to one-half-inch in diameter that often form a cymelike cluster. It grows up to two feet high on stiff, erect, many-branched stems. There are actually about 20 species of Pycnanthemum native to North America, but P. virginianum is one of the most common. Found in upland woods and meadows from Maine to North Dakota and south to Georgia, it is not considered showy enough for most gardens, but can be dramatic if you encounter groupings in the wild.
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