Tuesday, December 07, 2021

Trees and drought

by Barbara Guilland, WSU Grant-Adams Master Gardener
| November 21, 2021 1:00 AM

Losing a tree that has grown for years at your home is a sad event. Over the past few years, our springs and summers in the Columbia Basin have been warmer and so have our winters.

Research has shown that planting one tree to the west and one to the south of a house can significantly reduce energy use. It’s also important to know that some trees do better in our hot, dry climate than others. There are recommended pines, spruces, maples and other species at your local nursery. If you choose to grow a tree not native to the environment, it is important to know what to do to keep it healthy and green for its long life, a lifespan that is greatly reduced by drought conditions. Gardeners should become aware of the gradual changes that occur to trees as they experience drier, windier winters.

Drought conditions may vary from year to year. There can be short-term damage from one dry spell that will cause wilting, leaf scorch, and leaf loss, but if there is too little moisture over a period of years, you will begin to see other signs of not enough water reaching the root system such as stunted growth, branch die-back, and death. Stem dieback occurs when the soil under the tree dries out in hot summer months and continues to be dry during the winter months. During the early stages of a drought, the tree increases the number of fine feeder roots it grows as it searches for water, but if the drought period continues through the year, the fine roots die and are not able to take up water when it finally is available. The result may be that branches in the upper canopy of the tree die.

The bad news for some homeowners is that many trees, especially evergreens, can take up to three years to show the symptoms of inadequate water. When a tree is weakened by drought, insects such as wood borers and bark beetles can invade it. The presence of these kinds of pests is a sign of a weak tree. Some pests, like aphids, spider mites and lace bugs, which do not ordinarily harm a tree, begin to take away from the appearance of the tree as the tree loses its ability to grow new twigs and leaves faster than the insects can damage them. The tree’s root system’s ability to take up water is out of balance with the normal rate of growth of the tree’s branches and leaves. Injuries do not heal well and other diseases like cankers can invade.

The practical thing is not to wait until there are signs of drought damage, but to anticipate tree needs. Incorporate organic matter into your soil. Weed regularly – some healthy weeds are actually an indication of good soil, but you don’t want them taking moisture away from your tree! Water deeply (as much as 12 inches for some trees) rather than frequently. Use soaker hoses or drip methods rather than watering overhead. Apply mulch properly around the base of your tree.

If you have lost a tree or if you simply want to add a new one to your property there are many trees that do well in our area. You will find tree lists on Eastern Washington Master Gardener websites.

Master Gardeners are on call 24/7 year-round to answer gardening questions. Contact the WSU Grant-Adams Master Gardeners at the WSU Grant County Extension office, Phone: 509.754.2011 Ext. 4313 or Email: ga.mgvolunteers@wsu.edu.