Home & Garden Tips
Drought-stressed trees are cause for concern
By Roosevelt McWilliams County Extension Agent

One of the unfortunate adages of human nature is "out of sight, out of mind." This is particularly true when it comes to landscaping and gardening.

As long as we don't see a problem we are not too concerned with taking the necessary steps toward prevention. We are seeing this now as our trees struggle to cope with the effects of a hot, dry summer. Many homeowners overlook proper watering until the leaves begin to scorch or drop. Particularly susceptible to this neglect are older established trees.

Water shortage damages young and old trees alike, and set-up healthy trees for other problems. Drought conditions can lead to tree decline, pest problems and non-recoverable damage. Trees weakened by dry conditions are also more susceptible to wood borers, such as pine bark beetles whose infestations are more severe during drought.

Curling, rolling, mottling, scorching, chlorosis, shedding and early autumn coloration of leaves are drought responses in many deciduous trees. In conifers, yellowing and browning of needle tips may be seen. Dogwoods are some of the first trees to show drought stress with scorched leaf margins. Black cherries and birches wilt readily. Yellow popular, sycamore and buckeye are notorious for shedding leaves during summer droughts.

Interestingly enough, some stressed trees don't shed their leaves until after they become rehydrated. Depending on the tree species, drought stress can cause problems in the upcoming growing season such as poor bud formation and improper shoot elongation.

I have looked at a lot of oak trees in the county this year that have shredded their leaves or are dying out. They just can't take the compounded effects of environmental stresses, possible compacted soils and many other problems that plague older trees. Most established trees will recover on their own by dropping old leaves and putting on new growth. Some trees, such as tulip poplars, may go dormant earlier this year in comparison to past years.

Ideally, trees should be watered by soaker hose or drip irrigation. Water the soil directly beneath the tree canopy. Do not water beyond the drip-line and do not water closer than three feet to the trunk on established trees.

You should use a light organic mulch to conserve moisture to decrease competition from the roots of other plants. Remember to leave several inches between the mulch and the trunk to prevent crown rots.

Trees require 1 to 3 inches of water per week to maintain good health. Five gallons per square yard is about 1 inch of water. As with lawns, this should be applied in one deep watering each week rather than several shallow waterings. Light watering encourages shallow roots which can lead to increased root damage during time of excessive temperatures and drought.