Many calls have come into the Extension Office about trees dying in home landscapes, particularly oaks. More often than not the cause is related to drought stress. The damage caused by the recurring droughts of last 10 to 15 years result in trees in yards and open forests declining, and even dying throughout East Texas and the rest of the state.
Unfortunately, there is little that can be done to reverse the process of a dying tree. For future drought-related problems, if you catch them early enough, it might be possible to save your trees through judicious watering and fertilization. Drought stress also can be relieved by removing weeds and grass - which compete for water - beneath trees and replacing with a three-to-four inch cover of mulch.
Early signs of drought damage are yellowing leaves and premature leaf drop all over the crown. As the damage progresses, leaves will die from the bottom of the tree upward and from the inside of the canopy outward. Sometimes leaves simply wilt, or "burn" along their edges.
Trees need a deep, thorough soaking once a week during the growing season. A watering schedule that is adequate to maintain a lawn will not maintain a tree. A rule of thumb during a drought is to give small, one-year-old trees 28 gallons of water a week, two-year-olds 56 gallons a week, and three-year-olds 112 gallons.
Marty Baker, a retired Texas AgriLife Extension Service Horticulturist , recommended applying water in a donut-shaped pattern starting about five feet from the base of medium to large trees, to about five feet beyond the tree's dripline. Use a soaker hose and let the water flow for several hours once a week. Some species, such as post oak and bur oak, require less water; research your specific tree species for appropriate amounts.
Many trees, especially hardwoods, are harmed by herbicides used in the lawn and garden. Trees already stressed by drought can be killed by a heavy application of herbicide in the root zone. Avoid soil-activated herbicides around trees and always, always read the label directions.
Kathy Fiebig, former Smith County Master Gardener
Texas AgriLife Extension Service