Southern lawns require special grasses known as warm-season grass. Where cool-season grasses are mixed to provide sun and shade coverage, warm-season grasses have some adaptability to both and their use is dictated by climate and salt-tolerance. Clemson University's Extension Service explains that each grass is best-suited to a specific geographic range. Sun and shade tolerances are adapted to conditions within these ranges.
Warm-season grasses begin growing very early in the season and become dormant only for a month or two, or when a winter freeze arrives. Cool season grasses grow most actively in spring and fall; they enter dormancy in the hottest part of summer and in mid-winter. In the South, cool-season grasses that survive are called "transitional" grasses.
Warm season grasses grow from Virginia south and across the Southwest to Baja California. American Lawns and the Lawn Care Guide maps show transition grasses growing across the states bordering the Mason-Dixon Line from Virginia across Tennessee, Missouri to Southern California. On Clemson's map, tall fescue is the widest range of the transition grasses.
Transition Zone Grasses
American Lawns lists four major transitional grasses and a new hybrid called Thermal Blue. Kentucky bluegrass thrives in full sun. Perennial ryegrass is shade tolerant. Newer varieties of tall fescue grow throughout much of the South and adapt to sun and light shade. Cool season grasses complement the growth patterns of warm season grasses. Ryegrass is often used for over-seeding in areas where it will extend growing seasons through winter. American Lawns claims that certain Zoysia grasses grow as far north as Maryland.
Bermuda grass is a favorite grass in the South, noted for its drought resistance as well as partiality to full sun. It must be mowed shorter than most grasses, making it perfect for turf on golf courses and athletic fields. Buffalo grass is a native grass of the Great Plains and new hybrids are being successfully planted in sunny areas across the Southwest and Southern California. St. Augustine grass is sun-tolerant. Bahia grass grows best in sunny areas and is moderately drought-tolerant. It loves humidity, making it a Florida favorite. According to Clemson University Extension Service, St. Augustine, hybrid Bermuda grass and Zoysia grasses must be planted using sod or plugs.
The University of California rates red fescue and St. Augustine grasses as most shade tolerant, followed by Zoysia grass, kikuyu grass, tall fescue, Kentucky bluegrass, perennial ryegrass and Bermuda grasses. St. Augustine grass begins to thin in dense shade; it is native to the Caribbean and grows best in Southeastern coastal areas. Zoysia grass grows well into the transitional zone; its dense growth makes it unsuitable for overseeding with ryegrass or other cool-season grass. Centipede and carpet grass are both moderately shade-tolerant grasses. Bahia grass is tolerant of some shade.