Drought Stress in Trees
Watering Trees
Drought and high temperatures are a one-two punch to trees. Trees exhale moisture from their leaves in a process called transpiration. As temperatures climb, transpiration kicks into overdrive. During a drought, there isn’t enough water in the soil to replenish the water lost. When this happens, trees adopt survival strategies that can stress and weaken them.
If Mother Nature doesn’t provide at least an inch or two of rain each month, you can help your trees by watering. While frequent, light watering is sufficient for lawns and vegetable gardens, trees aren’t carrots and their moisture needs are different.
Trees need a slow, thorough soaking at least once a month. Most water is absorbed by roots in the top 6 to 12 inches of soil. These water-gathering roots extend outward from the trunk in all directions at relatively the same distance as twice the height of the tree. However, you can concentrate your watering from the trunk out to the tips of the tree’s branches. This critical piece of real estate is called the drip line.
There are several methods you can use to give your tree a drink. One is to turn your garden hose on a slow trickle and leave it in different zones within the drip line until each is soaked. Another method is to spiral a soaker hose out from the trunk. Maintain a 2-foot spacing between each successive coil, and be sure to extend the spiral out to the tips of the branches. To test if enough water is reaching the roots, push a piece of re-bar down into the soil. If you can penetrate 6 to 12 inches, you’ve probably provided adequate water.
Some trees need a little more TLC during a drought. Keep a close eye on drought-sensitive species such as magnolias, Japanese maples, dogwoods, beeches, tulip trees and birches. Also pay close attention to container plants and newly planted trees. Because they haven’t had time to establish extensive root systems, they are more vulnerable to periods of high temperatures and low rainfall.
Last, don’t forget to mulch. Mulch is any tree’s best friend. Besides minimizing evaporation of soil moisture and limiting rainwater runoff, mulch also protects the tree from mower and weed trimmer damage. Apply 2 to 4 inches of organic mulch around the root zone, taking care to keep it off the trunk.
With a slow, thorough soaking at least once a month and a little bit of mulch, the only worry you’ll have with your trees is deciding which ones to tie your hammock under.
