By Jeff Floyd
Certified horticulturist and arborist
Landscape irrigation is an art based on experience as much as it is a science. If it were as simple as dropping a hose in the grass, the lawn care industry wouldn’t exist in the form it does today. However, to distill it to its most basic element, Texas lawns need about one inch of water per week. But there are big differences in water quality, differences in the water requirements of various plants, differences in soil types and differences in seasonal evaporation.
When Texas landscapes receive rainfall, homeowners can subtract that from their overall irrigation needs for the week. If your property receives one-half inch of precipitation on Monday, then for the next seven days your landscape only needs another half-inch of supplemental irrigation assuming your water is of average quality. If you use well water, you should know that a large percentage of wells drilled in West Texas produce salty water. Salt buildup in soil can cause plants to become stressed by drawing water out of their roots. One way to minimize this is by adding more of that same salty water to wash the salts past the root zone. The additional amount needed is known as the leaching fraction.
Cacti and succulents have mechanisms that allow them to survive long periods without water. But your lawn doesn’t have to be filled with thorns and rocks. There are plenty of plants, known as xeric species, that tolerate drought. Bermudagrasses, yaupons, live oaks, salvias, lamb’s ears, oleanders, and many other beautiful species are capable of acclimating to dry conditions. Considering nearly sixty percent of summer water use goes into the landscape, and as much as half of that is lost to evaporation, designing xeric plants into your lawn can be as economical as it is attractive.
If your lawn is sandy, then water moves through it fast. To prevent plants in sandy soils from drying out, you’ll need to water them more frequently but in smaller amounts. They still only need an inch per week. Fortunately, most west Texas lawns are classified as sandy loam. Sandy loam soils have enough small and medium-sized particles to hold adequate moisture while still allowing for proper drainage.
Texas summers can be brutal. June, July and August temperatures strip moisture out of the landscape quickly. One way to reduce water loss is to irrigate early in the morning so that all your watering is completed before the sun comes up. Never water in the middle of a hot windy day. So much water is lost to evaporation this way that any benefit is usually offset by the expense. Finally, train yourself to know how the plants in your lawn look when they are well-watered and how they look when they are water stressed. Also, learn to use your finger to feel the soil. After a summer of sticking your finger in the dirt, it will become calibrated as your most reliable method of knowing when to irrigate.
