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I have started many articles by stating I don't know when the article will be published. One reason is that papers print our articles as a favor to us and only if there is space in the week's publication. I am writing this article the first week in June after the driest May since the dust bowl days. One thing that has helped is the cool weather. In fact, it's been so cool that we had frost for five straight nights. All plants have suffered from the dry weather, especially trees and shrubs that have been suffering due to dry weather for summer, fall, and going into winter for the past few years.

There are some things home owners can do that will increase trees' chances of making it through drought periods. Mulch around your trees with four inches of organic mulch to reduce moisture loss. Use wood chips, shredded bark, leaves or evergreen needles, but avoid the use of stone or rock near trees as this increases air temperatures and moisture loss from leaves and stems. Be sure to pull back the mulch six inches away from the trunk.

Don't fertilize a tree that is under drought stress as the salts in fertilizer may burn roots when there is not enough water. It may also stimulate top growth resulting in too much leaf area on the plant for the root system to maintain during periods of limited soil moisture.

Keep your trees healthy and pest free. Postpone any construction activities planned near your tree to reduce impact to the roots. If your tree has any insect or disease problem that may be adding additional stress, treat them accordingly to reduce the overall stress to your trees. Remove broken, dead, insect-infected, or diseased branches, as they can further weaken a tree during a drought period. Many tree species are harmed by herbicides used in the lawn so avoid heavy application of herbicide in the root zone.

Since watering is so important one needs to prioritize watering needs for different types of trees. The first trees to consider watering are those that will be most vulnerable and affected by dry conditions. Newly planted and young trees (one to seven inches in diameter) are not yet established and have a limited root system. These trees need more water even when we are not experiencing drought conditions. Generally it will take one full year per inch of trunk diameter to get established. The next priority is trees growing within a restricted root zone. Examples are trees adjacent to a driveway or house, growing within a landscape strip between your sidewalk and the street, or growing in a medium or traffic circle. Next, trees that have recently received root injury due to construction work will need supplemental watering because the root system has been stressed.

Most people don't understand how the root system works. Tree root systems consist of large perennial roots and smaller, short-lived, absorbing roots. The large, woody tree roots and their primary branches increase in size and grow horizontally. At least 90 percent are located in the top 12 inches of the soil. Root functions include water and mineral conductions, food and water storage, and anchorage.

In contrast, absorbing roots, although averaging only one-sixteenth inch in diameter, constitute the major portion of the root system's surface area. These smaller roots grow outward and upward from the large roots near the soil surface, where minerals, water and oxygen are more abundant. Large roots and small absorbing roots occupy a large area underground. The root system of a tree extends outward well past the drip line, up to two to four times the height of the tree.

For any other Lawn and Garden questions, please call our Extension office at 651-213-8905. If no one answers, please leave a voice mail message and we will get back to you.

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