HORTUPDATE - July / August 1998
In this issue . . .
Plant of the Month: Althaea, Rose of Sharon
Plant Tubes Cook Out in Texas
Announcements
Accent the Fall Landscape with Vegetables and Herbs
Pre-Vacation Planning Days
Rosemary Adds Interest to Texas Gardens
Growing Fruit
Xeriscapes Conserve Water
Dried Flowers
Garden Checklist for July / August
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Horticultural Update is published by Extension Horticulture, Texas Agricultural Extension Service, The Texas A&M University System, College Station, TX. Contributing Editors: Drs. Samuel D. Cotner, Vegetables; George F. McEachern, Pecans & Grapes; William C. Welch, Landscape; Douglas F. Welsh, Landscape
Editor July / August 1998: William C. Welch, Landscape Horticulturist
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JULY / AUGUST PLANT OF THE MONTH: ALTHAEA, ROSE OF SHARON
By Dr. William C. Welch, Landscape Horticulturist, Texas A&M University, College Station, Texas
Most Southerners have childhood memories of althaeas. They were once one of the most popular ornamental shrubs in our region. My memory is of a huge double-pink specimen planted at the side of my grandmother's home in south central Texas. It must have been fifteen feet tall and almost as wide. From May through most of the summer it was laden with double, fluffy pink flowers. Anyone who seriously wanted a plant could root 10- to12-inch stems during the winter by putting them into any good garden soil, and watering them every few days if rain was lacking. The cuttings were usually ready to transplant the next fall.
Althaeas grow quickly and need little attention. They thrive in the heat of summer and require only occasional deep watering to keep them growing and blooming. Native to China and India, they have been cultivated as long as records exist. The Chinese used the flowers and leaves for food. Thomas Jefferson grew them from seed, and was documented to have planted them at all three of his homes. Colors range from white to pink, lavender, and reddish purple. Several kinds have dark-colored centers in the flowers, and single-flowering types are quite common. Seedlings often sprout in nearby areas. Propagation from cuttings is usually preferred, because unlike seedlings, rooted cuttings will be exactly like their parents.
Althaeas are cold hardy over most of the nation. About the only serious problem is cotton root rot, which can kill plants of any age, and for which there is no practical control. Cotton root rot is mainly a problem in alkaline soils. Bud drop may occur when plants are under stress from too much or too little water. Newly planted althaeas should be watered every few days, like most other plants. Specimens located in sunny areas bloom much better than those planted in the shade.
The National Arboretum released several new althaeas in the 60s and 70s. These are all sterile triploids that have larger, earlier flowers, but they set no seed. Cultivars include ÎDiana' (white), ÎHelene' (white with maroon throat), ÎMinerva' (lavender), and ÎAphrodite' (pink). Another cultivar released a number of years ago is ÎBluebird', which is a single-flowering lavender-blue color. All these newer introductions tend to be more compact in form than the species types, and I find them better adapted to the northern half of Texas than the south.
Wherever you live, althaeas are a good possibility for use as large, deciduous hedges or specimens. Heavy pruning promotes vigorous growth and flowering, but creates unsightly stubs. By removing lower limbs flush with the main trunks, althaeas may be used as small trees, much like crape myrtles. Almost every southern nursery that sold ornamental plants in the 19th century listed althaeas. They probably deserve wider use in today's gardens, as we seek drought-tolerant, easily grown plants that provide color over a long season. Few non-native plants are as well adapted to our area.
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PRE-VACATION PLANNING
By Ted Fisher, Cherokee County Extension Horticulturist
Now that summer has arrived, you may be thinking about taking that well-earned vacation. If you are planning to take an extended trip now or later this summer, be sure your landscape is in order prior to leaving. Lawns, gardens, and landscapes left unattended for several weeks can be ruined by our summer sun, wind, and heat. Just a little extra effort on your part before leaving can make a big difference in the health and well-being of your plants.
Here are some practical tips that should help ensure that your home landscape will not suffer the post-vacation blues.
Water. Water the home grounds well prior to leaving. Soak your lawn, gardens, and all landscape plants deeply. Our shallow soils can dry out rapidly even after heavy watering, so if you will be gone over a week, plan to have a neighbor hook up your hose and do a little supplemental watering.
Cut. Mow your lawn a day or two before your leave. Use the same cutting height that you normally do. Don't lower the mower blade for a 'closer shave'. Doing so could easily cause sun scald and damage. If you plan to be gone more than a week, it would be a good idea to arrange to have a friend or neighbor mow the lawn for you.
Prune hedges and other plants likely to get gangly by the time you return.
Be sure that walks and flower beds are neatly edged before your departure. A buildup of growth while you are away will be difficult to manage on your return.
Mulch. Mulching helps conserve valuable moisture needed for plant growth while you are at home or away. Choose a clean mulch, free of weed seed, and one which will remain loose and well aerated. Consider grass clippings, pine bark, compost, or a variety of other organic materials. Mulching will also reduce or eliminate the weeding problem.
Check for insects and diseases. Spray, if necessary, for insects and diseases to prevent a buildup of pests during your absence. Summer insects and diseases do not take a vacation, and will work overtime on your healthy plants. This goes particularly for chinch bugs. Make sure you have applied chinch bug control to your St. Augustine lawn, or you just might find it severely damaged by this little critter when you return.
Harvest. Pick all ripe or nearly ripe fruit and vegetables. If you will be gone over a week, arrange for a friend to pull and use produce. Vegetables left unpicked will frequently cease to bear.
Maintain equipment. Take lawn and garden equipment by the repair shop if needed. They will have it ready by the time you return.
Protect Property. Arrange for a neighbor to pick up newspapers, or ask the paper delivery service to hold them until you return. Newspapers scattered over the front lawn are a dead giveaway that no one is home.
Lights on a timer are a good idea, and can provide an impression that someone is home.
Have a nice trip knowing that things at home will be in fine shape when you return. And don't forget to visit some gardens while you are away. There are many spectacular gardens to enjoy in just about any part of the country where you may be headed.
Landscape preparation for a summer vacation may sound like a lot of extra work, but it is really not much more than the normal weekend routine of maintaining a healthy, well-groomed landscape.
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ANNOUNCEMENTS
LANDSCAPE DESIGN STUDY COURSE: September 28 - 30, College Station. Contact the Extension Horticulture Office for registration form and program: (409) 845-7341
TEXAS & SOUTHWEST GREENHOUSE GROWERS CONFERENCE: November 10-13, 1998, Hilton Hotel & Conference Center, College Station, Texas. Call (409) 845-7341 for information
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ACCENT THE FALL LANDSCAPE WITH VEGETABLES AND HERBS
By Dr. William C. Welch, Landscape Horticulturist, Texas A&M University, College Station, Texas
Now is an excellent time to evaluate the home landscape and begin making preparations for fall plantings. Vegetables and herbs can be used in imaginative ways to add beauty, interest, and utility to our landscapes. Midsummer and early fall offer us a good 'second season' for growing these plants if gardeners can motivate themselves to provide a little extra care during the long, hot days of late summer. Hanging containers of parsley, mint, thyme, rosemary, and tomatoes can all be started now. These plants may be available at local nurseries, but with a little extra effort they can be grown from seed. Each has a drooping growth habit which makes it especially appropriate for hanging-container use. An even larger variety of herbs and vegetables may be grown in the more 'down-to-earth' containers, such as clay pots and wooden tubs. Tomatoes, peppers, lettuce, eggplants, carrots, and radishes are just a few of the many. Even small porches and decks of apartments can be made more attractive and interesting with groupings of containers filled with herbs and vegetables.
Two important points to consider in growing container plants are the media and the container selection. Most vegetables require excellent drainage, so select a container with a hole in the bottom. Plain clay pottery is attractive and versatile, as are many of the cedar and redwood tubs. Small containers dry out very quickly, and sometimes require daily or twice-daily irrigation. A minimum size for containers is 10 to 12 inches, with 16 or 18 inches being more appropriate for large plants such as tomatoes or eggplants. The media must also drain well for most plants to thrive and yet still hold an adequate amount of water. Some gardeners prefer soilless mixes, such as half peat moss and half vermiculite. Others like the added support of micronutrients found in mixes such as one-third garden loam, one-third peat moss, and one-third sharp sand. Many different media can be used successfully. The most important factor is for the gardener to learn how to manage the media selected, since water and fertilizer requirements vary considerably.
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PLANT TUBES COOK OUT IN TEXAS
By George Ray McEachern, Professor and Extension Horticulturist, Texas A&M University, College Station, Texas
June 30, 1998
The wine industry gave birth to a new concept of young vine protection and training in the late 1980s called 'plant tubes'. These are colored, thin-plastic sleeves which are placed over newly planted vines in February or March before growth begins. The concept is to protect the young vine from wind, wildlife, and post-emergence herbicide damage. The plant tubes would also act as a mini greenhouse in cool climates, and stimulate faster growth in the early part of the season.
In Texas, plant tubes become very hot, and stop growth because of high temperatures. Grape growers have had to remove the tubes as early as June to prevent vine death. Plant tubes have been successful in cool-climate vineyards, and they are now being marketed for all types of plants; but, Texas growers should be cautious when using plant tubes, and frequently check the plant trunks for heat damage.
Many types of plant tubes are now on the market. Some are blue, some pink, some green, some white, but most of them are light green. Some are made of thin wall foam covered with plastic. Some are cut flat at the bottom, while some are cut at a 45 degree angle. Some are a true tube, while others can be snapped or tied. These can be removed in the middle of the summer, and used again next year. Some plant tubes are 18 inches tall, while others are 48 inches tall, and some can be cut to the desired length.
In Texas, two forms of trunk protection have been used for over 20 years on pecans: aluminum foil or white latex paint, mixed 1 to 3 with water. The aluminum foil was first used in Extension demonstrations to prevent ROUNDUP herbicide damage to the trunks of newly planted pecan trees. George Madden of the USDA started the use of white paint for herbicide protection. Each of these systems also provides sunlight reflection in the fall and winter, which reduces trunk warming followed by lower-trunk freezing on the south or southwest sides of the tree. This type of freeze injury is called 'sunscald', and it is very common in Texas on young, non-bearing pecan trees. The benefits of foil or white paint come from a cooling effect rather than warming. The foil also prevents unwanted shoot growth close to the ground, and reduces rabbit damage; however, its main purpose is, and was, for protection from post-emergence herbicides. When ROUNDUP became cleared for use on peaches, the foil became widely used for the same purpose.
In California thirty years ago, two other forms of trunk guards were used -- waxed-paper milk cartons and waxed butcher paper, tied with a string. The waxed milk cartons caught on, and are still used by many wine growers. These two could also be used in Texas because they also reflect light. Any type of plant tube which reflects light should suffice in Texas.
In cold or cool climates, such as Bordeaux, France or Napa, California, the use of plant tubes is very positive. In addition to stimulating growth in the beginning of the season, they protect the trunks from herbicides and from rabbits and other animals; in grapes, they also direct the trunk in a straight, upward line, which reduces some vine training normally done by hand. However, in Texas, spring and summer temperatures inside plant tubes are too hot, and they actually retard growth rather than stimulate it.
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ROSEMARY ADDS INTEREST TO TEXAS GARDENS
By Dr. William C. Welch, Landscape Horticulturist, Texas A&M University, College Station, Texas
Many landscape plants suffer during the dry heat of August, but rosemary (Rosmarinus officinalis) thrives on it. Although usually cold-hardy in South Texas, some winter protection may be needed elsewhere in the state. Rosemary grows well even in poor, dry, rocky soil as long as drainage is good.
The evergreen character of the narrow foliage and many horticultural forms of the plant make it quite useful. Prostrate selections are good for ground cover or spilling over retaining walls. Mature height ranges from 18 inches to 4 feet, depending on the variety and growing conditions. Small lavender-blue flowers in spring and summer are attractive but not spectacular. A major attraction of rosemary is the strongly scented foliage which is popular, fresh or dried, for seasoning. The fresh tops are reported to be used to distill the aromatic oil used in perfumery and medicine.
Rosemary has been a popular plant for centuries in Europe, and was often planted close to the entrance of homes in the traditional cottage gardens of England. When people passed by and brushed against a rosemary plant, the scent was released and enjoyed.
Rosmarinus officinalis is a native of the Mediterranean region. Typical of many plants in that part of the world, old specimens may be thinned to expose the gnarled stems, which create a bonsai-like effect.
Few herbs can compete with this plant for landscape value. Propagation is by seed or cuttings. With the renewed interest in herbs, many garden centers now stock rosemary. One-gallon-size plants establish quickly. Full sun or partial shade are both good exposures. The key to successfully growing R. officinalis is well drained soil. If your soil is not well drained, try growing the plant in a clay pot or whiskey barrel half. Recently, interest in trimming rosemary into various topiary forms has increased. Tree standards are particularly nice. 'Arp' is probably the most cold-hardy selection of rosemary.
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GROWING FRUIT
By Calvin G. Lyons, Retired Extension Horticulturist, Texas A&M University, College Station
Now is the time to decide whether or not to grow fruits or nuts. Consider the time, labor, logistics, and chemicals involved in producing these crops. Are you willing to do what must be done to insure production? Do you have a suitable location? Fruit, such as blackberries, figs, Japanese persimmons, and pears, are low-maintenance crops. The hardest to care for are peaches, plums, apricots, and pecans.
For maximum production, fruit plants need at least 6 hours of full sunlight daily. Extremely shaded landscapes are not ideal sites for fruit planting.
Soil and drainage are also important considerations. Most fruit and nut species cannot tolerate excessive periods of 'wet feet'. Fruit trees planted in soil with poor drainage show reduced growth, pale green leaves, iron chlorosis, zinc rosette, leaf abcission, and in some extreme cases, drought stress. These symptoms occur when there is not enough oxygen available in the soil, and the plant is unable to absorb the essential nutrients necessary for growth, even though it may be standing in water. Growing trees and shrubs on large, raised beds can improve soil drainage where the native soil is unsuitable.
To evaluate soil drainage, dig a hole 32 inches deep, 8 inches in diameter, and fill it with 7 gallons of water. If it is empty within 1 hour, your site as excellent internal drainage. There is very good internal drainage if the hole is empty in 8 hours. If the hole is empty in 24 hours, there is good internal drainage. If the hole is empty in 48 hours, you have adequate soil drainage. At the end of 48 hours, if the hole still contains water, it will be extremely difficult to produce regular crops of high-quality fruits on that soil.
Peaches and plums need very good soil drainage. Apples, pears, and grapes need good soil drainage, while pecans, figs, and persimmons can survive with adequate soil drainage.
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XERISCAPES CONSERVE WATER
By Dr. Douglas F. Welsh, Landscape Horticulturist, Texas A&M University, College Station
Every plant in the nursery or garden center can be used in a Xeriscape landscape. It is not which plant you use, but where you put it.
Three different plant zones can be incorporated into a Xeriscape: A regular Watering Zone, an Occasional Watering Zone, and a Natural Rainfall Zone.
Regular Watering Zone: Plants in this zone require watering once every week or more, once established, in the absence of rain.
Occasional Watering Zone: These plants would require watering once every two or three weeks, once established, in the absence of rain.
Natural Rainfall Zone: Plants in this zone would require only natural rainfall, once established.
By zoning the plants in the landscape according to their water requirements, you prevent the situation of having to over water one plant type to meet the needs of another.
Each region of Texas has a palette of plants to choose from which are adapted to the soil, temperature extremes, and pest problems of the area. The challenge for both the professional and amateur gardener is to categorize the plants, based on expected water requirements. By using the categories of natural rainfall, occasional watering, and regular watering, most gardeners can find the best place in the garden for the plants in their region. For example, in much of Texas (areas of 30-plus inches of rainfall), the following categorization is often used:
Regular Watering Zone: Turf grasses, and annual flowers.
Occasional Watering Zone: Perennial flowers, and tender woody shrubs and vines.
Natural Rainfall Zone: Tough woody shrubs and vines, and all trees.
All plants have a place in a Xeriscape landscape. Visit your nursery or garden center today, and start creating your own beautiful, water-conserving landscape.
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DRIED FLOWERS
By Wayne R. Pianta
For hundreds of years, gardeners have preserved flowers by drying. The so-called 'everlasting' types, like straw flowers, have been most popular, but there are many other annual flowers that can be used. Summer annuals that are excellent for drying include marigolds, salvias, cosmos, zinnias, coreopsis, and gloriosa daisies. Ageratum, dahlias, calendulas, chrysanthemums, dianthus, asters, and daisies also make fine dried specimens. Many native flowers and plants, such as cattails, dock, oats, and numerous grasses, dry naturally or produce interesting seed heads. Flowers can be preserved by hanging, pressing, or drying with various drying agents.
Hanging. Air drying, or hanging, is the easiest and best method for preserving many flowers. Remove the leaves on the flower stem, and hang the flowers upside down in a warm, dry place until dry. An attic, closet, or pantry work well for flower drying.
Pressing. This method is quick and easy, but it flattens the flowers. For pressing, use unglazed paper, such as newsprint or an old telephone book. Place the flowers between several thicknesses of paper, making sure they do not overlap. Weigh down with a heavy object. This method takes from 2 to 4 weeks.
Drying with Absorbants. Flower can be dried by burying them in sand mixed with borax, cornmeal mixed with borax, or silica gel. These materials work well for drying certain flowers, but are undependable for others. Silica gel has the capacity to quickly absorb a large amount of moisture. Flowers, minus leaves, should be buried in the gel in a closed container, and left for about one week. Silica gel can be used over and over by re-drying it, after use, in a warm oven. The gel can be purchased in most garden centers, nurseries, florist shops, and hobby shops.
After drying, secure each flower to a wire stem by using a 2- to 4-inch section of Number 2 florist's wire; then, wrap all wire with green floral tape, and make your arrangement.
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GARDEN CHECKLIST FOR JULY / AUGUST
By Dr. William C. Welch, Landscape Horticulturist, Texas A&M University, College Station, Texas
Caladiums require plenty of water at this time of year if they are to remain lush and active until fall. Fertilize with 21-0-0 at the rate of one-third to one-half pound per 100 square feet of bed area, and water thoroughly.
Prune out dead or diseased wood from trees and shrubs. Hold off on major pruning from now until midwinter. Severe pruning at this time will only stimulate tender new growth prior to frost.
Sow seeds of snapdragons, dianthus, pansies, calendulas, and other cool-season flowers in flats, or in well-prepared areas of the garden, for planting outside during mid-to-late fall.
Plant bluebonnet and other spring wildflowers. They must germinate in late summer or early fall, develop good root systems, and be ready to grow in spring when the weather warms. Plant seed in well-prepared soil, one-half inch deep, and water thoroughly.
Picking flowers frequently encourages most annuals and perennials to flower even more abundantly.
It is time to divide spring-flowering perennials, such as iris, Shasta daisy, oxeye, gaillardia, cannas, day lilies, violets, liriope, and ajuga.
Make your selections and place orders for spring-flowering bulbs now so that they will arrive in time for planting in October and November.
Don't allow plants with green fruit or berries to suffer from lack of moisture.
A late-summer pruning of rosebushes can be beneficial. Prune out dead canes and any weak, brushy growth. Cut back tall, vigorous bushes to about 30 inches. After pruning, apply fertilizer, and water thoroughly. If a preventive disease-control program has been maintained, your rose bushes should be ready to provide an excellent crop of flowers this fall.
It is not too late to set out another planting of many warm-season annuals, such as marigolds, zinnias, and periwinkles. They will require extra attention for the first few weeks, but should provide you with color during late September, October, and November.
Establish a new compost pile to accommodate the fall leaf accumulation.
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