Tidewater Gardening - September 2007

Preparing for Fall - Drought Stress


K. Marc Teffeau

   As we are all aware, we are coming out of a very tough summer for plants in the landscape. Because of the drought conditions, some homeowners are finding trees and shrubs in their yards just up and dying. While newly planted trees and shrubs seem to take the brunt of the seasonal dryness, I have noticed that there are a number of fairly mature trees in both landscapes and in the woods that seem to have succumbed to the lack of water, especially oak trees.
    In many cases the death of the established trees is not directly due to the drought. There are a number of diseases and wilt organisms in the soil that infest tree roots. During normal weather years, adequate moisture is present in the soil so that the trees are not stressed and the disease is kept at bay. However, when we get into a drought situation like we have now, the stress put on the tree is so great that the established diseases just take over.
    Another source of the die back is the presence of “lawnmoweritis.” This is a fairly common occurrence in home and commercial landscapes where, at some point in time, damage was done to the base of the tree by the careless use of the lawn mower. This damaged trunk area allowed an entrance point for various canker-causing organisms to enter the cambium layer of the tree stem and become established. This condition seems to be especially present in landscapes which are maintained by some lawn mowing companies who employ wannabe NASCAR drivers to ride the mowers.
    Whether the problem is a soil-borne wilt disease, or a trunk cancer, the result is the same. The tree’s “plumbing” is damaged resulting in the tree’s inability to translocate water and nutrients from the roots to the leaf canopy. The prognosis for these trees is fatal, so you will need to resign yourself to the fact that the browning maple in your front yard is not going to come back and that there is no magic spray or chemical that you can use to restore it to health.
    If the entire leaf canopy and not just the edges of the leaves are brown, then there is no hope. If just the leaf margins are brown or yellow, the tree may be suffering a condition called leaf scorch and it may be able to weather the weather, as it were. In this case, additional watering is recommended to help maintain the tree. It will be critical, if these dry conditions continue into the fall, that you water trees, evergreen shrubs and newly planted trees and shrubs on a regular basis into the early winter. A drought-stressed plant that goes into the winter will suffer winter damage and may die next spring.
    If it is September, it must be yellow jacket time. These pesky wasps have left their jobs of feeding their young and building the nest and are actively foraging for sweets. They’re at picnics, in the garbage, and anywhere food may be. They especially like to hang around aluminum can recycling bins where they feed on the left-over cola and sweet syrup residue left in the soft drink cans.
    The yellow jacket nests are at their peak populations now and will usually be found in the ground. How many of us have had the unfortunate experience of running over a nest in the ground while mowing the grass? An Olympic track star has nothing on me in the running area when a mess of yellow jackets decide to work on the ankles! The nest entrance will be busy with many foragers coming and going, but individuals may fly hundreds of yards in their search for the sweet stuff.
    Yellow jacket colonies do not over-winter like honeybees do. With the arrival of cold weather, any remaining males and the old queen die. The new queens will over-winter and start new nests in the spring. The old nest will not be reused next spring.
    The best control of yellow jackets is to eliminate the nests when found. An aerosol wasp and hornet insecticide applied to the nest in the evening when the nest is quiet is the best control. Repeat applications may be necessary if there is still activity.
    If the nest is in a building, do not seal the entrance. The insects could chew another entrance to the inside. Another effective control is to eliminate access to food sources. Cover or remove garbage, pet food and leftovers from outside meals. Don’t leave empty soda cans lying around.
    There is no good area control for the scavenging yellow jackets. Traps eliminate a few individuals, but only a small percent of what’s in the nest. If the nests are not in high traffic areas they can be left alone and allow the cold weather to kill off the nest. You may be tempted to try the redneck yellow jacket control method – pouring gasoline into the nest and tossing a lit match into the hole. Please don’t do that! This practice is dangerous to the applicator and also pollutes the ground.
    If you have caladiums in the landscape, as the nights become cool, they will begin to loose leaves. Dig them up, allow them to dry, and store them in a warm, dry place. Replace them with fall mums and add another source of color to the landscape.
    Perennial phlox should be divided about every third or fourth year. Early fall and early spring are the best times to plant and transplant them. Divide big clumps into thirds.
    Plant roots of both garden and tree peonies in September or early October so they will have time to become established in the soil before winter. Dig a hole about 18 inches across and 18 inches deep for each tuber. Space the holes so that the plants will be at least 3 feet apart. Make sure the roots are buried only 1½ to 3 inches below ground level. Deeper planting keeps the plants from blooming.
    As you plant your spring bulbs, remember that a mass planting of one flower type or color will produce a better effect than a mixture of many colors. Flowers of bulbs stand out more vividly if displayed against a contrasting background. For example, white hyacinths among English ivy, yellow daffodils against a ‘Burford’ holly hedge, or red tulips towering over a carpet of yellow pansies.
    Sowing seeds of hardy annuals, such as sweet alyssum, pinks and sweet peas now will give the seedlings time to get established and develop good root systems before the coldest part of winter. This gives them a head start on growth and flowering next spring.
    September is an excellent time to establish new perennial flower beds. Dig, divide and replant overcrowded beds of cannas, day lilies, violets and Shasta daisies. Spread a liberal amount of organic matter, such as compost or bulb fertilizer, over the area. Mix this into the soil at least 6 to 8 inches deep. Space divisions at least 1 foot apart in all directions so that root competition will not be a problem for several years.
    Don’t forget to add lilies to the plants in the perennial beds for many years of beautiful flowering. Modern hybrids are available in many colors and grow from 2 to 6 feet tall. American-grown hybrid varieties have less trouble with virus diseases than the old species types.
    For established deciduous trees and shrubs in the landscape, wait for their leaves to begin to drop before fertilizing them. This signals dormancy, when no new growth will be stimulated that might not harden up prior to cold temperatures. If we continue to have a dry fall, I would recommend forgoing fall fertilization for this year. As I mentioned earlier, it is more important to water the plants adequately.
    Fall fertilization of deciduous trees and shrubs is usually recommended because, although the upper part of the plant has grown dormant, the roots are active until the soil temperature drops below 40°, so nutrients will be taken up and used by the plants to develop a stronger root system.
    Also, do not prune at this time. Excessive pruning now will quickly delay the hardening process that has already begun in anticipation of winter several months ahead. New growth that results from pruning can be easily injured by an early freeze.
Happy Gardening!