Southern California presents challenging environments for traditional and nontraditional lawn grasses. Delineated by county lines running straight across the state, the region consists of California's 10 southernmost counties and spans U.S. Department of Agriculture plant hardiness zones 6 through 11. Choosing the most suitable grass for your lawn requires balancing aesthetic preferences with environmental needs and other considerations. Many factors, including seasonal dormancy and response to heat, drought and salt, influence choices for Southern California lawn grasses.
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Dormancy and Color
Getting the look you want hinges on understanding how and when grasses grow. Some grasses, called warm-season grasses, actively grow during the summer. These include coarse-textured, shade-tolerant St. Augustine grass (Stenotaphrum secundatum), which generally grows in U.S. Department of Agriculture plant hardiness zones 8 through 11. When temperatures drop below 50 degrees Fahrenheit, warm-season grasses go dormant and turn brown. In contrast, cool-season grasses have their most active growth period from fall through spring and tolerate colder temperatures. As long as temperatures stay above 32 F, cool-season grasses such as sun-loving Kentucky bluegrass (Poa pratensis), suitable for USDA zones 3 through 8, keep Southern California green. St. Augustine goes dormant by late fall, and may die in temperatures below 10 F.
The high temperatures that make SoCal famous can be tough on lawns. Warm-season grasses flourish at high temperatures that turn cool-season grasses brown and dormant. Though slow to establish, traffic-tolerant zoysia grass (Zoysia spp.), which grows in USDA zones 6 through 10, has excellent heat tolerance paired with disease resistance. The medium-textured, warm-season grass turns uniform beige in winter, but some find the color appealing. Finely textured, cool-season bent grasses (Agrostis spp.), which grows in USDA zones 4 through 8, struggle in high heat when their shallow roots cry out for frequent watering. Kentucky bluegrass becomes susceptible to disease and weeds and can go dormant in high-heat, low-water conditions.
Water conservation and water costs increasingly influence Southern California turf choices. Fast to establish and quick to recover, warm-season Bermuda grasses (Cynodon spp.), which grow in USDA zones 7 through 10, thrive in full sun and high temperatures. With roots reaching up to 6 feet deep, even at manicured lawn lengths, Bermuda grasses withstand extreme drought and improve soil's water-holding capacity. Deep-rooted Buffalo grass (Buchloe dactyloides), which grows in USDA zones 5 through 9, has excellent drought tolerance but extended winter dormancy. Not surprisingly, heat-loathing, high-maintenance bent grasses and Kentucky bluegrass fail to hold up well in drought, with roots reaching just 4 to 18 inches deep.
Grass responses to saline soil and water are important for inland Southern California as well as coastal areas. Salt tolerance pairs closely with drought response. Soil salts and saline irrigation water affect aesthetics and survival, as soluble salts pull water away from grass roots and create droughtlike conditions. Pet urine causes the same response. Warm-season seashore paspalum (Paspalum vaginatum), which grows in USDA zones 8 through 11, combines exceptional salt and heat tolerance with short winter dormancy and aggressive growth. Bermuda, zoysia and St. Augustine grasses all have excellent saline tolerance. Bent grasses are among those most vulnerable to saline damage and turf disease.