Managers of landscapes in most urban areas of California are facing mandatory or voluntary water conservation requirements. The following questions and answers provide answers to some common questions about managing and conserving water in landscapes.  

Q. How much water can be saved by removing all or part of a lawn?
A. Water savings depends on the type of turfgrass the lawn is, which plants, if any, will replace it, and how well the water applied to new plants is managed. If plant material is changed but irrigation practices are not, then little water savings will be realized. Turfgrass water requirements vary by species. Warm-season lawns, such as bermudagrass, zoysiagrass, and St. Augustinegrass, need about 20 percent less water than widely planted cool-season lawns, such as tall fescue. So, simply replacing a tall fescue lawn with a warm-season one will significantly reduce the water needs of a turf area. Warm-season grasses can remain alive and largely green, though not lush, when irrigated at the same level as trees and shrubs.

Q. Will lawns or landscapes suffer if they are not irrigated every day in the summer?A. Established lawns and landscapes do not require daily summer irrigation except in a few extremely hot inland and desert areas that also have sandy or decomposed granite soils. Only newly planted lawns and landscape plants are likely to be damaged by not receiving daily summer irrigation.

Tall fescue lawns can perform well when irrigated 2 to 4 times per week in the summer, while bermudagrass and other warm-season lawns can usually be irrigated less frequently. Trees, shrubs, and groundcovers will perform well when irrigated every 5 to 10 days. Follow the approach described in the answer to the next question to reduce irrigation days and conserve water.

Q. How much can irrigation be reduced without hurting a lawn?
A. It depends on the species of grass that dominates the lawn and the amount of water currently being applied. If the lawn is primarily tall fescue or another cool-season grass and it is being well watered with no obvious drought symptoms or brown areas, then the amount of water can probably be reduced by 10 to 15 percent without seriously injuring it. You may see brown areas develop over time after reducing water by this amount, however. Brown areas that develop in lawns when water is reduced are often a sign that the irrigation system applies water unevenly rather than that the amount of water is too little to meet the turfgrass’s needs.

If the lawn is predominantly bermudagrass or another warm-season grass and you are keeping it well watered, you can probably reduce the amount of water by up to 25 percent without seriously hurting it. If the lawn already has brown areas from too little water, then reducing the amount of water further may cause serious damage or death. Always gradually reduce the amount of water applied following the approach described above.

Q. How long will it take a lawn to die from lack of water?

A. If you stop watering a lawn, it will gradually turn brown signifying it has died or become dormant. Depending on weather conditions, this may take from 1 to 6 weeks for most lawn grasses, but it might take longer for deep-rooted grasses like bermudagrass. The first signs of inadequate water will be wilting of grass blades and a blush-gray appearance. Next, leaf blades will yellow and eventually become brown. The lawn will probably not turn from a uniform green to a uniform brown, but will instead look mottled with green, yellow-green, gray, and brown areas. A lawn that recently turned brown from drought can often be revived with regular, thorough watering.

Q. If a lawn dies, or is damaged due to drought, when should it be replanted?
A. Do not replant a lawn until there is enough water available from rainfall, irrigation, or a combination of the two. Assuming water is available, the best time of year to plant lawns is in the fall or spring for cool-season turfgrasses (tall fescue, rye, etc.) and late-spring or summer for warm-season turfgrasses (bermuda, zoysia, St. Augustine).

Q. How often should a lawn area be watered?
A. Irrigation frequency for a lawn depends on climate, soil type, and the grass that dominates the lawn. Generally, for best performance during summer, lawns in coastal areas planted with tall fescue, kentucky bluegrass, or ryegrass (cool-season grasses) will need irrigation one to three days per week, while those in inland valleys will need summer irrigation three to five days per week. Sites where soil is sandy or where turf roots are restricted will need to be irrigated at the more frequent end of these ranges and those with relatively clayey soil or planted in Bermudagrass, buffalograss, st. augustinegrass, and zoysiagrass (warm-season grasses) will need irrigation at the less frequent end of theses ranges. Lawns in desert areas are normally planted with a warm-season grass and need irrigated 3 to 7 days a week in summer, depending on soil type and root depth . Run the irrigation system long enough to wet the root zone of the grass on each irrigation day. Irrigation frequency should be gradually reduced from fall through winter and then increased again from spring into summer.

• Questions and Answers About Water Conservation and Drought in the Landscape - UC