Plant of the Month
By Dr. William C. Welch, Landscape Horticulturist

The giant rose mallow has the largest flowers of any hardy perennial. Some of the hybrids may be one foot in diameter. Rich, moist soil and full sun bring the most vigorous growth, but mallows are very accommodating, and will tolerate light shade and less desirable soils. Giant rose mallows will flower from seed the first year if started very early in spring. Favorite cultivars may be rooted from cuttings during the growing season. Colors range from crimson, white, pink, rose, and in-between. Giant rose mallows are relatives of the native hibiscus found in Louisiana, East and Centra Texas, and other Gulf South states. They are among the most spectacular and easily grown plants for use in the border. Following the spring and summer growing season, the plants freeze back to the ground each fall. Old stems should be cut back to a height several inches above the ground. New shoots emerge by mid-spring, and the plants quickly develop handsome mounds of foliage and flowers by early summer. Individual flowers last only a day, but each plant may flaunt several flowers at once. Numerous seedling selections, such as 'Southern Belle' and 'Frisbee' are offered in good seed catalogs. Few garden plants provide so much enjoyment for so little care. Seeds of giant rose mallows are available from catalogs, while container-grown plants are usually in stock at Texas garden centers and nurseries. Color selection is possible when you purchase blooming-size plants. If growing giant rose mallows from seed, it is important to start them early in the season so that they will have adequate time to develop before freezing weather sets in. Hibiscus mutabilis is an old-fashioned perennial or shrub hibiscus better known as the Confederate rose. It tends to be shrubby or treelike in Zones 9 and 10, though it behaves more like a perennial further north. Flowers are double and are 4 to 6 inches in diameter; they open white or pink, and change to deep red by evening. The 'Rubra' variety has red flowers. Bloom season usually lasts from summer through fall. Propagation by cuttings root easiest in early spring, but cuttings can be taken at almost any time. When it does not freeze, the Confederate rose can reach heights of 12 to 15 feet with a woody trunk; however, a multi-trunk bush 6 to 8 feet tall is more typical. Once a very common plant throughout the South, Confederate rose is an interesting and attractive plant that grows in full sun or partial shade, and prefers rich, well-drained soil. Several years ago, Dr. Jerry Parsons, Extension Horticulturist in San Antonio, released a new giant rose mallow named 'Moy Grande' from the San Antonio Botanical Garden. 'Moy Grande' has huge flowers of dark rosy pink. Best availability is in the San Antonio area.

Lawn and Garden News
By Dr. William C. Welch, Landscape Horticulturist

Texans are fortunate to have a number of flowering annuals available that will withstand our hot, dry summers. Marigolds, zinnias, periwinkles, cleome, portulaca, gloriosa daisies, and globe amaranth are all extremely heat-tolerant, and well adapted to our environment. Castor beans will provide huge masses of tropical foliage in green, bronze, or purple, with minimum effort. For shaded areas, chose from impatiens, begonias, caladiums, or coleus. All these are available in a variety of foliage or flower colors to suit most any scheme. Moonflowers and morning glory vines may be planted from seed now, and when grown in arbors, provide shade and flowers later in the summer. Summer is a time for enjoying the landscape. By carefully selecting and placing colorful, easy-to-grow annual flowers, you can make our outdoor areas more attractive, and still have plenty of time to relax.

By Dr. Larry A. Stein, Extension Horticulturist, Uvalde

I am always amazed at the number of folks who have never used drip irrigation, much less know what it is! In working with drip irrigation on day-to-day applications on fruits, pecans, and vegetables, I have come to take it for granted. However, its use is not nearly as widespread as I once thought. In this day and age, when water is in the spotlight as a critical resource, there is a great potential for water conservation using drip irrigation. Drip irrigation, also commonly known as trickle- or micro-irrigation, is merely the precise application of water where and when plants need it. The concept is not new, as the Germans and Italians worked out the basics in the 1930s, and, according to Dr. Jody Worthington, former TAES Research Horticulturist who did extensive research on drip irrigation, Texas Extension specialists in the 1940s were showing growers how to make concrete lines to sub-irrigate gardens from windmills. However, it took the development of UV-light resistant plastic pipes and fittings to make drip irrigation practical for home gardeners. The greatest selling point for drip irrigation in its earliest applications was that great savings in water could be realized. Some sources claimed plants under drip required only a third as much as water as usual. These erroneous assumptions have caused tremendous headaches in the industry. A plant‚s water requirements are the same regardless of how the water is applied. Initially, water savings are realized when plants are small, and only a small volume of soil must be wet. However, as plants grow, more and more soil volume must be wet for drip to be effective. The real conservation features of drip irrigation come from the precise application of water and minimal runoff, less evaporation from an essentially closed system, and less water lost to weeds and undesirable plants, since the system is placed exactly where the desirable plants need it.

The basic component parts of a drip irrigation system are as follows: (1) water source (well or city), (2) filter, (3) delivery lines, and (4) emitters. The water source used will dictate the amount of filtration needed. If the water is sandy or dirty or from an open pond, there is a greater need for filtration as opposed to using city water. Although it is best to filter city water, it can often be used unfiltered without too much problem. However, the life of the lines and emitters can be prolonged using filtration.

Basically there are two types of drip emitters. In one, the water path is very long thus reducing the amount of water which comes out of the emitter. The other type utilizes a very tortuous or crooked path. Emitters are also designed to be either low- or high-pressure. Low-pressure emitters usually apply one to two gallons per hour at operating pressures of 2 to 5 psi, whereas high pressure emitters typically apply one gallon per hour at 15 psi. Such devices can be purchased or made. Considering the low cost of emitters, it is best to purchase them. They can be placed at the desired spacing along a poly hose, or hose can be purchased which already have holes or emitters within. Three common types are Bi-wall, At@ tape, and Ram tubing. The hose with pre-formed holes works extremely well for garden applications. Spacing between holes varies with the product; 12-, 18-, and 24-inch spacing is common. There are many drip irrigation products on the market. All are basically good, and there is no great advantage of one over another, but regardless of how good the products are, they all eventually stop up. Drip systems must be maintained and cared for, as with other water systems; hence, it is best to leave the emitter and loops on top of the ground so they can be checked regularly. The most practical applications for drip irrigation in the home landscape are in gardens, hedge rows, shrub or flower beds, and combinations of these along with trees. The key to making drip irrigation work in home landscapes is in scheduling -- knowing when and how long to water. The best absorptive roots for most plants are in the top 6 to 12 inches of the soil, since this upper soil area contains a lot of oxygen. The deeper one goes into the soil, the less oxygen is present, and root growth is less. In order for water to be absorbed by the plant, oxygen must be present. If oxygen is not present, plants cannot take up water, and the roots will drown if the saturated conditions continue. An irrigation system should never be operated for longer than 8 to12 hours a day. In no case should the system be turned on and forgotten. Some turn the system on for 24 hours, or until the water reaches the surface (buried systems), and then leave the system off for several days. Such operations present extreme wet and dry periods which are deleterious to plant growth. An ideal situation is to maintain uniform moisture and oxygen in the soil. In garden applications, the hose with holes is laid down the plant row. One hose will work for two rows of vegetables, or emitters can be placed at each transplant. Either way, the plants or seeds are well watered at planting, and then left alone until regular growth begins, unless it is very dry. The system should maintain uniform moisture down the plant row. If saturated conditions occur, the time interval between watering will need to be increased. Generally speaking, when using drip around hedges, one emitter per plant is sufficient. The hose and emitters are placed around the shrubs at planting, and are used to maintain uniform moisture as needed. The hose can be tied into lawn sprinkler systems or operated manually. Hose with holes, hose with emitters, or micro-sprinklers can be used for flower beds. Basically, the size and shape of the bed will dictate the system employed. Remember to water early in the morning to avoid excess humidity and disease pressure. Tree applications begin with emitters but are usually best served later with micro-sprinklers. As the best absorbing roots are at the dripline of the trees, the emitters need to move out as trees grow. This requires hose loops with emitters, which can cause problems with maintenance operations. Hence after 5 years, micro-sprinklers which wet the area covered by the canopy of the tree work best. Micro-sprinkler heads can be changed as the tree grows, to provide greater water coverage. The key with trees is to wet as much of the tree root system as possible, but maintain water in the top 18 to 24 inches of the soil. Drip irrigation is a wonderful, labor-saving and water-conservation device for the home owner. For some, such devices have been the salvation for their gardening efforts. Many wish they had discovered it years ago, and wonder how they made it before. Most large nurseries and seedsmen carry drip irrigation kits, which can be purchased to get a feel for how the system works. These same folks carry supplies to upgrade and increase the range of your drip irrigation system.

The Landscape Design Study Courses are a series of four courses offered approximately six months apart in the Bryan-College Station area. They are accredited by the National Council of State Garden Clubs, and cosponsored in Texas by the Texas Agricultural Extension Service. Although the courses are a four-part series, participants may begin with any of the four. Master Gardeners are finding the courses a logical extension of their training and a good opportunity to receive in-depth information in the field of landscape design. Course II is being offered September 27-29, 1999 at the Brazos Center in Bryan. Subjects to be addressed at Course II include: History of Landscape Architecture, The Private Garden, Landscape Architecture Design Process, Plants in Composition, Site Design and Ground Forms, Art and Nature Appreciation, Introduction to Urban Design, and a special-interest lecture on Making Organic Gardening Work for You. Faculty are selected from the Department of Landscape Architecture at Texas A&M University, horticulturists, planners, and professional landscape architects. Of special interest for Course II will be two lectures by Dr. Neil Odenwald, Professor Emeritus and former head of the Department of Landscape Architecture at Louisiana State University. Registration information for the course may be obtained from Lenora Sebesta [(409) 845-7341 in the Extension Horticulture office] or Jacque Hand [(409) 845-7692 or (409) 845-8904 in the office of Conferences and Short Courses at Texas A&M University]. Rooms are being reserved at several local motels for participants.

This article by Van Bobbit and Dr. Val Hillers appeared in „Down the Garden Path Newsletter,š published by Purdue University.

Pathogens (microorganisms which cause disease) can be transferred from animal manures to humans. The pathogens Salmonella, Listeria, and E. coli, as well as parasites such as roundworms and tapeworms, have been linked to applications of manure to gardens. Publicity about illnesses due to E. coli 0157:H7 has made people more aware of the potential risk of foodborne illness from manure contamination. As a result, many are now asking whether it is safe to use manure on their gardens. In August 1993, The Lancet medical journal reported on a small E. coli 0157:H7 outbreak that appeared to be the result of manure applications to a garden. The gardener ate eggs and milk products, but no meat, and her diet relied heavily on vegetables from her garden. She fertilized the garden all summer with manure from her cow and calf. No E. coli 0157:H7 bacteria were isolated from fecal samples taken from the cow and calf; however, the animals did have antibody counts for the pathogen, suggesting they had been previously infected. E. coli 0157:H7 was isolated from the manured garden soil. So, how risky is the use of manure in gardens and compost piles? If you use fresh manure in the garden, there is a risk that pathogens which cause disease many contaminate garden vegetables. The risk is greatest for root crops, such as radishes and carrots, and leafy vegetables, such as lettuce, where the edible part touches the soil. Careful washing and/or peeling will reduce some of the pathogens responsible for the disease. Thorough cooking is most effective. To reduce the risk of disease, we suggest these precautions:

+ Use only aged or composted manure in the garden.
+ Never apply fresh manure after the garden is planted.
+ Thoroughly wash raw vegetables before eating.
+ Do not use cat, dog, or pig manure in gardens or compost piles, because some of the parasites which can be found in these manures may survive, and remain infectious to people.
+ People who are especially susceptible to foodborne illnesses [pregnant women, very young children, and persons with chronic diseases, such as cancer, kidney failure, liver disease, diabetes, or AIDS should avoid eating uncooked vegetables from manured gardens.

Garden Checklist
By Dr. William C. Welch, Landscape Horticulturist

+ Take a critical look at your landscape while at the height of summer development. Make notes of how you think it can be better arranged, plants that need replacement, overgrown plants that need to be removed, and possible activity areas that can be enjoyed by family members.
+ Check for insects and diseases. Destroy badly infested plants. Spider mites can be especially troublesome at this time. Select a chemical or organic control, or use insecticidal soap.
+ Supplemental irrigation is essential for many ornamental plants such as coleus, caladium, geranium, dahlia, azalea, and camellia during the h, ot dry summer days ahead. Water lawn and garden thoroughly, but not too frequently. As a general rule, soak to a depth of 8 inches. Finish watering by early afternoon, to lessen the chance of disease.
+ During the summer, soil moisture becomes extremely important and essential for good plant production. Because continual watering is oftentimes costly and time consuming, it pays to conserve the moisture around plants. This is best done by mulching. A good mulch will retain valuable moisture needed for plant growth, and improve overall gardening success. Mulches are usually applied 2 to 6 inches deep, depending on the material used. In general, the coarser the material, the deeper the mulch. For example, a 2-inch layer of cottonseed hulls will have about the same mulching effect as 6 inches of oat straw or 4 inches of coastal Bermuda hay.
+ There is still time to plant some of the colorful, heat-tolerant summer annuals. Direct-seed zinnias and portulaca, and purchase plants of periwinkle, salvia, marigold, and purslane. Be sure to water transplants as needed until roots become established.
+ Removing faded flowers from plants before they set seed will keep them growing and producing flowers. A light application of fertilizer every 4 to 6 weeks will also be helpful.
+ House plants can be moved out of doors this month. Sink the pots in a cool, shaded garden bed to prevent them from drying out so quickly; water pots, container plants, and hanging baskets often. Monthly feedings with house plant fertilizer will encourage continued growth.
+ Now is the time to plan for next spring. Consider digging and dividing any crowded spring bulbs. Once the bulbs have matured and the foliage has turned brown, it is time to spade them up and thin out the stand. Crowded bulbs produce fewer and smaller blooms. They usually need thinning every 3 to 4 years.
+ June is the time to select daylily varieties as they reach their peak of bloom.
+ Fertilize roses every 4 to 6 weeks. Apply a high-nitrogen fertilizer immediately after a flush of bloom.
+ Continue to spray susceptible roses with a black-spot control such a Funginex every 7 to 10 days.
+ Re-blooming salvias, such as Salvia greggii and S. Farinacea, should be pruned back periodically during the summer. To make the job easier, use hedging shears, and remove only the spent flowers and a few inches of stem below. Fall-blooming perennials, such as Mexican marigold mint (Tagetes lucida), chrysanthemums, physostegia, and Salvia leucantha, should be pruned in the same manner during the summer to keep them compact, reducing the need for staking. This type of pruning should be completed prior to September 1, since flower buds begin forming about that time.

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