Healthy lawns require effort, plenty of water and nitrogen fertilizer. They also depend on the right choice of lawn grass. American gardeners have a wide choice of grass varieties; a good blend includes varieties that thrive in the weather, soil and percentage of sun and shade in a given yard. Most lawn grasses are perennial but annual grass has its place, too.
Annual lawn grass germinates, grows, produces seed and dies all in the course of one growing season. Perennial grasses have a longer life. They establish a crown and extend stolons or rhizomes during their first growth cycle, then alternate growth and dormant periods once or twice a year for at least three years. They will produce seed during each growth cycle. Most will spread vegetatively by crown growth or by establishing new crowns along stolons or rhizomes, specialized plant stems that grow on top of or just under the soil line.
Each perennial grass has from a few to dozens of varieties that are used in various regions of the U.S. When only one type of grass is planted, suggests Ohio State University’s extension, several varieties should be blended to balance the others’ adaptability in specific areas. Favorite types of perennial grasses include Kentucky bluegrass, perennial ryegrass, fine and red fescues, Bahia, centipede, St. Augustine, Bermuda grass and Zoysiagrass.
Annual grasses are primarily used for quick cover to shade slower-germinating perennial types in newly seeded lawns and for green cover during perennial winter dormancy. Only annual ryegrass is commonly used in lawns, but excessive annual ryegrass applications will crowd out the permanent perennial grasses. Annual bluegrass is considered an invasive weed. Other annual grasses are used for agricultural cover crops.
Weed grasses can be either annual or perennial grasses that are too coarse, thin or invasive to make an attractive lawn. Annual weed grasses like crabgrass and goose grass germinate and begin growing before perennial grasses in spring and are best managed with a pre-emergent herbicide. Perennial weed grasses like quack grass and nimblewill form crowns; they must be spot-treated with herbicides or dug out and replaced with new-seeded soil or sod. Tall fescue, once considered a weed grass, has been bred in several varieties that are now recommended for public parks and landscapes. Many weed grasses are useful as agricultural cover crops.
Warm and Cool Season Grasses
Bahia, buffalo grass, centipede, St. Augustine, Bermuda grass and Zoysiagrass are warm-season perennial grasses with single, extended growth cycles. Often green until December, they grow best in the South. Cool-season grasses like fescues, bentgrass, Kentucky bluegrass and perennial rye grow best in the northern third of the country. The middle, transitional zone of the country is home to a mix of warm- and cold-season perennial grasses, including tall fescue and Zoysiagrass. Transitional gardeners may overseed with annual ryegrass for extended green, especially when lawns are seeded with cool-season blends of Kentucky bluegrass and perennial rye.