Dr. Grow: How dry I am

A yew shrub is dying because of drought stress.

Drought stress has killed this pin oak tree.

Recently a friend and I were discussing things that needed to be done around our homes. He said that he had finally found someone to remove a dead pin oak that stood about 40 feet tall and was 18 inches in diameter. He thought that the tree died from the drought that occurred last fall and winter. He said he just didn't realize that a tree that large would suffer from drought.

My friend's experience is not an isolated example of the results of the drought that we are currently experiencing. I have had several people bring me samples from trees, shrubs and lawns which show symptoms of drought.

The first symptom expressed by drought suffering trees and shrubs is wilting on hot sunny afternoons. Plants demand a lot of water during that time of the day. When the sun goes down, plants demand less water. Quite often they will recover from wilting until the next afternoon. Then wilting will again occur.

If it doesn't rain, leaves of trees will then begin to scorch. The edges of leaves will turn brown. There will be no discoloration or margin between the green portion of the leaf and the brown or scorched portion of the leaf. A colored margin is an indication of a fungus present in the tissue.

If rain still doesn't occur or if no watering is done, deciduous plants will then begin to lose their leaves. This is a survival response to the lack of water in the soil. By losing leaves, the need for water is minimized. If water is applied soon enough after leaf drop, new leaves may sprout out on the plant.

Adventitious buds may also sprout on the trunks of deciduous trees when they have suffered from drought stress for a long period of time. These dormant buds along the trunk become active under extreme stress. Again, it is another survival response to stress.

Evergreen trees and shrubs, on the other hand, react differently to extreme stress. The chances of them budding out after leaf drop is minimal. They have no adventitious buds that become active during periods of extreme stress. It is extremely important to monitor these plants in your landscape so that they never get too dry.

I want you to be aware of one thing. The symptoms exhibited by plants that are suffering from drought stress are the same symptoms exhibited by plants that are overwatered.

When overwatering occurs, plant roots rot and become non-functional. Therefore the top of the plant reacts just the same as if it were under drought stress. The best way to tell the difference between a plant that is being overwatered and one that is suffering from drought is to put your finger in the soil. If the soil is dry drought is occurring. If the soil is wet, then you have been over watering.

I have found that plants located on slopes exhibit drought stress sooner than plants located on flat areas. When rainfall does occur, water runs off of the slopes while it tends to soak into the soil on the flat. More rainfall is needed to get the same results on slopes. I have also found that some species are more affected by drought than others. For example, many pin oaks have been damaged or killed by the current drought. I have also seen a lot of old yews damaged. Trees and shrubs that were under stress due to disease or insects have been lost by the current drought. The extra stress due to drought was more than they could withstand.

When someone finds that their trees and shrubs have been damaged from drought, they want to fertilize to help the ailing plant. Using a good tree and shrub fertilizer is important, but it is not a cure-all. More important, you must water, water, water, to overcome the damage due to drought stress.

You must water tree and shrubs under the entire area outlined by the drip line. Be sure to give the plant one to two inches of water each time you irrigate. How you apply water is not important. You can allow the hose to trickle near the stem for a long period of time. You can use a deep watering system such as a Ross root feeder.

You can use a water weeping hose or you can apply water with a conventional sprinkler. Make sure that the water is soaking into the ground and not running off of the surface. If your trees and shrubs are on a slope, then irrigate or sprinkle for a few minutes every hour for several hours. This will allow more water to enter the soil and not run off of the surface.

If drought continues, repeat the watering process every two or three weeks. This should keep your plants going until Mother Nature decides to give us an adequate amount of rainfall again.