Adjusting Landscape Maintenance to Conserve Water and Improve Drought Resistance
By Dennis Pittenger, UC Riverside
Adjusting and fine-tuning basic maintenance practices can greatly affect and maximize the drought resistance and water conservation potential of landscape plantings.
When water is limited, change the mowing height to at least 3.0 inches for tall fescue, ryegrass, Kentucky bluegrass, and other cool-season grasses. Likewise, raise the mowing height of Bermuda grass, zoysia grass, St. Augustine grass, and other warm-season grasses to at least 1.5 inches. Mowing height can be lowered after drought conditions pass or at the onset of cooler weather in the fall season. Also, be certain to keep mower blades sharp and always follow the one-third rule for mowing frequency: mow often enough so that no more than one-third of the length of the grass blades is removed at each mowing. For example, if a tall fescue lawn is maintained at three inches, it should be mowed when the grass height reaches no more than 4.5 inches. Following this rule ensures mowing does not cause scalping, which can severely injure the grass.
To improve the drought resistance and water conservation potential of established trees, shrubs, ground covers, and other non-turf landscape plants, forgo fertilizing them altogether. These plants have low fertilizer requirements, so routine fertilization, especially with nitrogen, can push excessive leafy growth that in turn demands added water.
During periods of severe water restriction, prune only to maintain formal hedges and remove broken, dead, poorly-structured or seriously pest-affected portions of trees and shrubs. Also, check all plantings frequently and trim away small portions that begin to block irrigation heads and emitters or that pose safety problems by blocking views or access to key areas.
Pruning limits the size of woody plants and ground covers but also creates wounds and removes food reserves stored in their stems. After pruning, plants attempt to close the wounds created and produce chemicals that prevent pathogens from entering the wounds and spreading through their tissues. These defensive processes require plants to use large amounts of energy from stored food and to grow vigorously. Plants that have been extensively pruned and that have limited water lack the ability to support these processes and close and defend wounds rapidly.
In turf areas that has been compacted by foot traffic or thatch buildup, aerate the area in the spring using a machine that forces hollow metal tubes into the ground and brings up small cores of soil to the surface.
Compacted soil and excess thatch restrict root growth and water penetration to roots. Aerated turf is more drought resistant, because it develops deeper roots. The aerated soil also allows rain or irrigation water to penetrate deeper into the ground.
Keep mulch six inches away from the bases of plants to avoid trapping moisture that favors disease development there. If overhead irrigation is used over mulched plantings, irrigate infrequently and be certain irrigation run-times are long enough for water to penetrate the mulch layer and wet the soil deeply. Soil should be wetted about 12 inches deep for trees and shrubs and slightly less than that for many non-turf perennial landscape plants.
Using Water Saving Products
In recent years, many new so-called water conservation products have been marketed to the landscape maintenance industry. Beware and always carry out your own evaluation before making large-scale use of any of these. Set up a test area in your turf or other plantings where simultaneous side-by-side treated and untreated areas can be compared. Attempt to keep all watering and other maintenance the same in both areas so that the only variable is the product being evaluated. Regularly observe and evaluate the test plantings and use the results to make your own judgment as to whether the product is beneficial before committing time and money to buy and apply it. Always adjust your basic maintenance practices as discussed above prior to using any new product because you might be able to maximize drought resistance and water conservation potential in your landscape plantings without it.
About The Author
Dennis R. Pittenger is a University of California Cooperative Extension environmental horticulturist who works at the UC Riverside Botany and Plant Sciences Department. His email: email@example.com.