During the summer months, it's best to focus your watering on plants that provide the greatest economic and environmental benefit to your homes — trees and shrubs. These plants provide us with shade, clean air, clean water and increased property values.
In most cases, well-established trees don't need much supplemental water. However, young trees and shrubs don't have a root system large enough to obtain sufficient water to survive during periods of extreme drought. Consistent additions of water are advised. It’s best to follow a prescription of frequent, consistent and light irrigations — aka the 3-2-1 method .
Mature trees require supplemental water only if normal rainfall is deficient in spring and early summer, or from March through July. Watering from August through October is not as important to long-term health. Overwatering is often as detrimental as a lack of water.
In confined spaces, such as between two driveways where soil is often limited, ¾ inch of water applied twice a month is recommended. In most areas, like front and backyards, one inch to one and a half inches a month will suffice. Normal rainfall fulfills the majority of needs. In both circumstances, a slow application is necessary to create a large water profile in the soil. Location is also important. For newly planted trees, apply only to the root ball. For mature trees, target the inside and outside of the drip line.
Water isn’t always the most important factor in tree health. It also helps to recreate the natural environment with frequent additions of compost and mulch. Compost is thoroughly decomposed organic matter from manures, vegetation or both that resembles rich soil. Compost may be incorporated into the soil. Mulch may be organic (wood chips, pecan shells, pine bark) or inorganic (small rocks, decomposed granite), but generally it’s organic material that has not decomposed.
Mulch is never ever put into the soil, but rather always placed on the surface. A nitrogen deficiency will result if too much carbon — the mulch — is incorporated into the soil, resulting in small, pale green leaves and reduced growth.
Apply a half-inch of compost in the spring and fall, and two inches of mulch in May and September. Cover as much of the root zone as possible to encourage roots to expand and soil to retain moisture.
Treat your trees right and they will treat you right for decades.
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About our expert
Mark A. Peterson is a conservation project coordinator for San Antonio Water System. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you’re likely to find him hiking San Antonio’s wilderness parks or expounding on the virtues of geography and history to his friends.
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