HORTICULTURAL UPDATE
September 1997
IN THIS ISSUE . . .
Plant of the Month: Coral Vine
Announcements
Rock Gardens
The Grand Magnolia
Tree Pruning
Success with Vegetables Takes Planning
Garden Checklist for September
Horticultural Update is published by Extension Horticulture, Texas Agricultural Extension Service, The Texas A&M University System, College Station, TX. Editor: Edna Smith, Designer: Jill Stavenhagen. Contributing Editors: Drs. Samuel D. Cotner, Vegetables; George F. McEachern, Pecans & Grapes; William C. Welch, Landscape; Douglas F. Welsh, Landscape
Editor September 1997: Douglas F. Welsh, Landscape Horticulturist
PLANT OF THE MONTH FOR SEPTEMBER: Antigonon leptopus, Coral Vine
By Dr. William C. Welch, Landscape Horticulturist
Texas A&M University, College Station, Texas
This native of Mexico is widely cultivated in Texas and the Gulf South for its striking, lacy pink flowers. Like many of our popular heirloom plants, it has at least several common names, such as 'heavenly vine' and 'rose of Montana'. It is a vigorous vine, with heart-shaped leaves, that needs the support of a trellis, fence, or tree. The first hard freeze of autumn kills all the top growth, but established plants return readily the next year from sweet potato-like tubers that some sources describe as edible. It is generally root hardy in the southern half of our state, and can be easily grown in containers elsewhere.
Coral vines are easily grown, but must have good drainage and at least a partially sunny exposure. They are very drought tolerant, and really begin their landscape display after the first good rains of late summer and fall. A white form is sometimes available. Propagation is by division or seeds. It is best to start the seeds early in the spring so that the vines will grow and develop tubers before frost.
A. Leptopus is an integral part of many southern gardens. At its best, it graces a garden like fine lace. The foliage is attractive and sufficiently dense to provide summer shade on trellises and arbors. I planted one in combination with a vigorous old climbing rose, and it is a very successful combination, with the rose ('Trier Rambler') having a pale pink color and the coral vine much darker. The rose provides support for the coral vine, and the combination is striking.
LANDSCAPE DESIGN STUDY COURSE II
College Station - September 22 & 23, 1997
This course is open to anyone interested in learning more about landscape design. The course is approved to satisfy the 12-hour continuing education requirement for Texas Master Gardeners. For program and registration form, contact Dr. William C. Welch at (409) 845-7341.
OKTOBER GARTENFEST: "Gardens Grow into Organizations"
Winedale, October 24 & 25
The fourth Winedale Gardening Symposium 1997 will focus on important gardening organizations and how they influenced pioneer gardens in Texas. The richness and diversity of our Texas gardening heritage is both a stimulus and a challenge for today's garden-maker. The most meaningful gardens of our past are those that reflected the life-style of their time and the individual styles and tastes of their owners, while clearly providing a sense of place. It is our goal at these programs to examine the contributions of gardening organizations and how they can help us select attractive and useful plants for today's gardens. Registration is processed through The University of Texas Winedale Historical Center, P. O. Box 11, Round Top, TX 78954. Contact Gloria Jaster for information on area lodging and registration at (409) 278-3530, FAX (409) 278-3531.
ROCK GARDENS
By Dwight S. Hall, Former Extension Horticulturist
Texas Agricultural Extension Service
With fall planning and planting just around the corner, the home gardener may well consider constructing a rock garden. Texas has an abundance of native rock, and the naturalistic effect of plants among rocks, trees, and garden paths may easily and aesthetically be a part of our overall landscape design.
The success of rock gardens in the landscape depends on a natural appearance. Never should they appear artificial or forced; they should be informal, as if nature provided a bit of beauty in the home garden. For this reason, the rock garden should be located away from the formal parts of the garden, in an area where the rocks will blend naturally with informal tree groupings and unusual soil mounding or soil banks.
The size of the rock garden will depend on many factors: the number of available rocks and plantings, the size of the surrounding area, and the time the gardener can give in constructing and maintaining the area. Because a well-tended rock garden demands a lot of attention and time, it is usually best to keep the area small. If too large, it is likely to suffer from neglect, and nothing is more unsightly than a poorly maintained rock area with weeds and drying plants.
In selecting rock, attempt to choose the same type and color, so as to have unity. Choose various sizes of rocks for a natural appearance. Never force the rock into an unnatural position; try to use local native rocks, which will give the appearance of belonging naturally to the area.
Place the rocks in groupings to form interesting angles. Leave void areas and pockets of various sizes and proportions for plantings and for visual relief from the irregular appearance of rocks. Be sure planting pockets are well retained to avoid wash and loss of soil from rains and waterings. An irregular site will allow for the best show of rocks and plantings, as the viewer will see various levels at each angle of observation. Planting pockets should be well worked during construction, as it may be difficult to prepare the soil without disturbing the rocks once they are placed in the design.
The best rock gardens are located in a shaded area or one exposed to only partial sun or filtered light; therefore, the area may well be constructed beneath large trees where grass may be difficult to maintain.
The rock garden is an ideal area in which to place garden features such as bird baths, fountains and pools, garden lighting, pottery, driftwood, and sculpture. The items of accent may be carefully planned for and so located as to blend in with the total visual appearance of the garden. Make sure that these accents do not dominate; they must appear natural and unforced.
The plantings, too, must be very natural and informal in arrangement, with pockets and mass plantings for year-round interest. Since the rocks must be the principal feature of the garden, plantings should be simple, and the area must not be over-planted. Ground cover plants, such as ajuga, sedums, English ivy, jasmine, violets, vinca, liriope, monkey grass, strawberry begonia, strawberries, and day lilies, lend themselves well to the naturalistic effect of rock areas. Dwarf plants, such as yaupon, dwarf hollies, holly fern, aucuba, dusty miller, dwarf bamboo, fatsia, fatshedera, dwarf junipers, dwarf sasanqua, Japanese black pine, mahonia, and Indian hawthorn, are of proper size to complement rock areas and provide a permanent evergreen interest. Seasonal plantings of spring bulbs, caladiums, moss roses, phlox, pansies, spider lilies, spring and summer annuals and perennials, and wildflowers will add color and interest.
Well-planned rock gardens can be fun and rewarding for the entire family, and will surely provide an unusual attraction in any home landscape.
THE GRAND MAGNOLIA
By Greg Grant, Extension Horticulturist, Cherokee County
Texas Agricultural Extension Service
Magnolia grandiflora! The most beautiful tree in the world; no picture and no painting can do thee justice; no description, and be it ever so glowing, can give an idea of thy natural and noble beauty. ö Henry Nehrling: "My Garden in Florida," 1944.
No other flower, perhaps no other plant, evokes images of the South like the magnolia does. It is the emblem of the Southern Garden History Society, and the state flower of Louisiana and Mississippi. This stateliest of the evergreen trees is native from Texas to North Carolina, and can obtain immense sizes (up to 100 feet!) in the wild on deep soils. Everybody who has ever seen this bold tree with its large glossy leaves and huge fragrant flowers has fallen in love with it. William Bartram made numerous references to the 'glorious magnolia' in the chronicles of his travels through the Southeast in the 1780s. According to Alice Coates in Garden Shrubs and their Histories (1964), huge native specimens were regarded by Michaux as some of the finest productions of the vegetable kingdom. She adds: "It is said that the Indians would not sleep under such a tree when in bloom because of the overpowering scent of its flowers, one of which, if kept in a bedroom, could cause death in a single night." I never realized Indians even had bedrooms! All early southern nurseries carried it, and almost everybody in the South grew it.
The genus is named for Pierre Magnol (1638-1715), professor of medicine and director of the botanical gardens in Montpelier, France. Of course, grandiflora refers to the huge flowers. In 1833, Herman Bourne refers to it as the 'big laurel' in his Florist Manual, and listed it along with sweet bay and rose bay (oleander). There were a number of early varieties, including floriosa with larger flowers, angustifolia and lanceolate with narrow leaves, rotundifolia with rounded leaves, and praecox which was early flowering. It was introduced into England around 1734 but never thrived there as in its home. I have learned through time that there is a gardening rule that says if it thrives in England, it won't grow in the South, and if it sulks in England, send her home to Dixie! The first magnolia to be sent to Europe, and the name-plant of the genus, was Magnolia virginiana, the sweet bay or swamp magnolia, also a native of the Southeast. It was formerly known as M. glauca. It was listed as such in John Bartram and Sons' 1792 catalogue with the description "charming -- the neat white rosette blossom possesses an animating fragrance . . . " According to Coates, it was introduced to England in 1688. William Cobett, who wrote The English Gardener in 1833, was obviously a fan. He said the fragrance was "the most delightful that can be conceived, far exceeding that of the rose; in strength equaling the jasmine or tuberose, but more delightful . . . none of the other magnolias are nearly so odoriferous as this; all but this are somewhat tender; this might be in every shrubbery in England with the greatest of ease, and I cannot help expressing my hope that it may be one day as common as the lilac." I think he stayed in the bedroom sniffing it a little too long. This was obviously before the introduction of the hardy oriental magnolias.
Other magnolias were cultivated in the early South as well, including three other southeastern natives: the cucumbertree magnolia (M. acuminata), the umbrella magnolia (M. tripetala), and the bigleaf magnolia (M. macrophylla). Bartram and Sons' Nursery carried the first two. Prince's Nursery of Flushing, New York listed Thompson's magnolia, a cross between the sweet bay and the umbrella, in their 1823 catalogue. In Breck's Book of Flowers (1851), Joseph Breck lists M. glauca, M. acuminata, M. auriculata, M. fuscata, M. conspicua, M. soulangiana, M. purpurea, and M. gracilis. The early-blooming, deciduous M. x soulangiana (saucer magnolia) became a mainstay in our southern gardens and one of my favorite childhood plants, which I knew as the 'tulip tree'. The LSU campus in Baton Rouge has beautiful specimens. The tulip tree is a cross of M. heptapeta (formerly M. denudata and M. conspicua), the yulan magnolia, and M. quinquepeta (formerly M. liliflora and M. purpurea), both from China and both encountered in the South. The white-flowered yulan magnolia was introduced to England from China by Sir Joseph Banks around 1879. There are very nice specimens scattered around Baton Rouge. The purple-flowered M. quinquepeta was introduced to England from Japan by Thunberg in 1790. Both parents and their 'child' are exceptionally beautiful. Prince's 1832 catalogue listed M. x soulangiana, while Parsons' 1876-77 catalogue listed M. x soulangiana "Lennei' and M. stellata, the star magnolia.
Magnolias require deep, acidic, well drained soils. Otherwise, they are easy to grow. Propagation is from stratified seed, fairly hard-to-root cuttings, or grafting. Even if it is just for the fragrance, everybody in the South should have a magnolia. I think it's the law.
TREE PRUNING
This article by Brad Abrameit, Extension Horticulturist and Master Gardener Coordinator for Rio Grande Valley, appeared in "Valley Master Gardeners," Vol. 1, No. 8, May 1997.
In April, at a tree pruning seminar held in Weslaco, Don Mueller, from the State Forest Service, gave an excellent presentation followed by hands-on pruning demonstrations. The information below is reinforced with material from that seminar.
--- DO NOT'S
Do not top your tree. Topping is unfortunately a common practice designed to encourage vigorous new growth. While that is achieved, the overall strength and structure of the tree are sacrificed. The limbs that are forced from latent buds are very often weakly attached, which makes them susceptible to wind damage. Pollarding is often confused with topping, but this practice is following by thinning, and is more technically demanding. Many Europeans utilize this practice to dwarf their trees.
Do not make stub cuts. Do not leave a portion of the branch sticking out; this will allow rot to enter more easily.
Do not remove all of the lower limbs on newly planted trees. This is sometimes referred to as 'limbing up'. Some of the lower branches should be left intact for a period of time to encourage caliper growth. No more than one-third of the top growth on younger trees should be removed.
Do not make cuts flush with the trunk or adjoining limb. The proper cut is made flush with the collar at the base of the branch. The collar is the somewhat raised area surrounding the branch union with the parent branch or trunk. This zone contains chemically-protective tissue; if it is cut off or severely cut into, proper natural 'healing' cannot occur. And, once this area is damaged, it is damaged for good. Trees have the unique ability to compartmentalize, or surround injured tissues with a protective barrier.
Do not cut large limbs with a one-cut method. This will surely result in bark peeling from the weight of the cut limb. Rather, use the three-cut method.
Do not use pruning paints or wound dressings. They do not encourage 'healing', nor do they prevent pathogens from entering the tree. Although they will not damage the tree, they will certainly prove to be an unwarranted cost. Painting could be justified where aesthetics are concerned. A dark paint can hide the glaring spots made from fresh wood being exposed from a recent cut.
--- DO'S
Do approach the tree, and look for any limbs that might be a hazard to someone underneath it or to a building or structure nearby. Broken branches, weak branches, narrow crotch angles, and other obvious faults should be identified. First and foremost, these limbs should be taken care of.
Do remove any dead or dying material on the tree.
Do remove limbs that are rubbing each other or cross over one another. Limbs that rub will develop wounds that attract insects and diseases.
Do remove excessive vertical sprouts. Some may need to be left in place to encourage caliper growth.
Do prune to encourage fruiting. In the case of fruit trees, thinning out of limbs will allow allocation of nutrients, etc., for fruit production. In addition, practices such as open-center pruning allow sunlight penetration for fruit ripening.
Do choose to keep branches with wide crotch angles. Wide crotch angles are generally from 40 to 90 degrees, and are very strong as a result of being composed of solid wood. Narrow crotch angles are less than 40 degrees, and contain a bark inclusion that causes them to be very weak. Narrow crotch angles should preferably be pruned out while the tree is still young. In older, established trees, bracing and cabling may be the only resort.
Do prune the tree to your liking. There are many different ways that one particular tree may be pruned. Even experts will have differing opinions on which branches to remove. The bottom line is: whatever you like is what you should do, so long as you utilize proper cutting techniques and pruning methods.
Do keep in mind that you should always have a reason for every cut that is made.
SUCCESS WITH VEGETABLES TAKES PLANNING
From "Hort 4 Fall 1996," published by the Texas Agricultural Extension Service.
Time to Decide. In most areas of Texas, gardening can continue year-round. It is always a tough decision to decide whether to terminate spring-planted vegetables or to carry them through until the first frost. In northern areas of Texas, many spring-planted crops, such as tomatoes, eggplants, and peppers, can be grown until the first killing frost, provided the plants remain healthy. In southern areas of the state, home gardeners should plant fall gardens anew rather than trying to carry spring-planted crops through the summer. During early fall, also plant flowering annuals that bloom in late fall, withstand winter temperatures, and bloom again next spring; this means preparing the soil and getting transplants started as soon as possible. Most gardeners overlook that fact that the best time to plant many flowers and vegetables is during the late summer and early fall months.
Planning. Planning is important in a spring garden, but it is a necessity in a fall garden if maximum productivity is to be achieved.
Fall vegetable crops are categorized as long-term and short-term crops. Duration of these crops depends upon when the first killing frost occurs and the cold tolerance of the vegetables.
Plant long-term, frost-tolerant vegetables together. Frost-tolerant vegetables include beets, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, chard, collards, garlic, kale, lettuce, mustard, onions, parsley, spinach, and turnips. As mentioned earlier, all flowering annuals recommended for fall planting are frost-tolerant.
Plant short-term, frost-susceptible vegetables together so that they can be removed after being killed by frost. Frost protection and the planting of a cereal rye cover-crop are facilitated if such a grouping system is used. Frost-susceptible vegetables include beans, cantaloupes, corn, cucumbers, eggplants, okra, peas, peppers, Irish potatoes, sweet potatoes, squash, tomatoes, and watermelons.
GARDEN CHECKLIST FOR SEPTEMBER
By Dr. William C. Welch, Landscape Horticulturist
Texas A&M University, College Station
Rejuvenate heat-stressed geraniums and begonias for the fall season by lightly pruning, fertilizing, and watering.
Caladiums require plenty of water at this time of year if they are to remain lush and attractive until fall. Fertilize with ammonium sulfate at the rate of a to 2 pound per 100 square feet of bed area, and water thoroughly.
Don't allow plants with green fruit or berries to suffer from lack of moisture. Hollies will frequently drop their fruit under drought conditions.
Prune out dead or diseased wood from trees and shrubs. Hold off on major pruning until midwinter. Pruning now may stimulate tender growth prior to frost.
Divide spring-flowering perennials such as irises, Shasta daisies, gaillardias, cannas, day lilies, violets, liriope, and ajuga. Reset divisions into well prepared soil with generous amounts of organic material worked into the top 8 to 10 inches.
Prepare the beds for spring-flowering bulbs as soon as possible. It is important to cultivate the soil and add generous amounts of organic matter to improve the water drainage. Bulbs will rot without proper drainage.
Plantings at this time can provide landscape color for three seasons in central, east, and south Texas. Annuals set out early enough will bloom as soon as Thanksgiving, and frequently last until Memorial Day. Annuals that should soon be available in nurseries and garden shops include petunias, calendulas, pansies, snapdragons, stock, sweet peas, and violas (from seed).
Continue a disease-spray schedule on roses, as blackspot and mildew can be extremely damaging in September and October. Funginex, used every 7 to 14 days, will usually give excellent control.
Christmas cactus can be made to flower by supplying 12 hours of uninterrupted darkness and cool nights (55 degrees F.) for a month, starting in mid-October. Keep plants on the dry side for a month prior to treatment.
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