As we move into the summer and the heat and the potential drought that can come with it, I have had more than a few questions from property and tree owners that all sound much the same: What can I do to ensure that my old trees will not only survive but do well through what may be another severe summer?
Lately, I have seen increased occurrence of stress indicators in older trees, especially oaks, that seem nonspecific in cause.
However, there is good reason to believe that much of this trouble is the result of heavy and frequent spring rains that saturated clay soils, followed by a period of drought. This one-two punch from Mother Nature has damaged some tree systems in their ability to take up critical water and metabolize important elements for normal function.
Fortunately, many of these trouble signs will probably abate with time, if we can get some moderate weather and rainfall.
Supplemental water will be important during dry, hot days when we have less than 1 inch of rainfall per week. The rule for supplemental irrigation is to water established trees once a week. Water them slowly for 2 or 3 hours at a time. To do this correctly, it may be necessary to operate an irrigation system manually or to use a system of soaker hoses. This will be especially important if your trees are on a slope where surface runoff is rapid.
While clay soil holds water tightly, it takes it up slowly. On a slope, you may have to turn your system on and off over several cycles to not end up watering the street gutters.
Standing water near old trees after a rain can be a bad sign. If necessary, consult with someone about effective evacuation methods. If you think your soil is too wet in a particular area, dig a hole a foot deep and about a foot wide. Fill it with water. If the water has not disappeared in 30 minutes, you have a problem that could be damaging nearby roots.
Mulching can go a long way toward improving survival and function of plant root systems during hot weather. When applied properly, mulch offers multiple benefits. It retains soil moisture, retards the competition of weeds and grass, gradually reverses soil compaction, moderates soil temperature, and can also esthetically improve the environment. Around your trees, about 2 inches deep is plenty. While old trees like good mulch much better than grass, do not pile the mulch around the bottom of the trunks, as this can retain moisture that facilitates root rot diseases.
Avoid pruning your elm trees during the summer. Elms are especially susceptible to infection through pruning wounds. Wait until October or November. And don't allow pruning crews to climb your trees with tree spikes on their feet, unless they're taking the tree down. Good trim crews don't need spikes.
Another pruning tip for summertime or anytime is to avoid removing more than 25 percent of a tree's leaves (or buds) during any growing year. Topping a tree should usually be avoided.
Certified arborist Fred Morgan of Cordova has owned and operated Morgan Tree Service since 1974, and is involved in arboricultural consulting, diagnostics and problem solving. His column appears in Home & Garden once a month. Get more tree info at .
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