Grasses used for lawns and turf are members of the Poaceae family, which also includes cereal crops. Turfgrass species form lawns, sports fields, and golf courses globally. The selection of the right turfgrass depends almost entirely on the local climate and the specific performance requirements of the lawn.
Primary Categorization by Climate
The most fundamental way turfgrasses are classified is by the temperature range in which they optimally thrive, resulting in the division between cool-season and warm-season grasses. Cool-season grasses grow best when air temperatures are consistently between 65 and 75 degrees Fahrenheit. Warm-season grasses require much higher temperatures, preferring a range of 80 to 95 degrees Fahrenheit for robust growth.
This climatic distinction dictates their geographical prevalence, with cool-season varieties dominating the North and warm-season types thriving in the South. The Transition Zone, a challenging area through the central band of the country, experiences hot summers and cold winters. Here, neither type is perfectly adapted year-round, often necessitating the use of specialized, blended varieties.
Common Cool-Season Grass Varieties
Cool-season turfgrasses are favored for their deep green color and ability to withstand freezing temperatures during winter dormancy. Kentucky Bluegrass (Poa pratensis) creates dense, attractive turf with a medium-fine texture and an emerald, blue-green hue. Although germination is slow, it establishes a high-quality, durable lawn once mature, making it a popular choice for northern lawns and sports fields.
Perennial Ryegrass (Lolium perenne) is frequently incorporated into seed mixtures because it germinates exceptionally fast, providing quick cover and helping to stabilize soil. It has a fine texture and high tolerance for foot traffic, but it is a bunch-type grass that requires overseeding to repair bare patches.
The Fescue group includes Tall Fescue (Festuca arundinacea) and Fine Fescues. Tall Fescue has a coarser texture but possesses superior heat and drought tolerance compared to Bluegrass, making it a viable option within the Transition Zone. Fine Fescues, such as creeping red fescue and chewings fescue, stand out for their exceptional shade tolerance, making them suitable for yards with significant tree cover.
Common Warm-Season Grass Varieties
Warm-season grasses withstand intense summer heat and prolonged periods of drought. Bermuda grass (Cynodon dactylon) is known for its fine texture, high-density growth, and exceptional tolerance to heavy foot traffic and scorching temperatures. It is the most aggressive and fastest-growing warm-season turf, but it requires full, direct sun and goes dormant quickly with the first sign of frost.
Zoysia grass (Zoysia spp.) provides a dense, carpet-like turf with a softer feel and a rich green color. It exhibits better moderate shade tolerance than Bermuda grass and is valued for its drought resistance and lower water requirements. Since it grows more slowly than Bermuda, Zoysia requires less frequent mowing, though its high density can lead to a buildup of thatch over time.
St. Augustine grass (Stenotaphrum secundatum) is characterized by its broad, flat blades and is the most shade-tolerant common warm-season type. It establishes a very thick turf that crowds out weeds, but it requires more consistent watering than Bermuda or Zoysia. This grass is also susceptible to certain fungal diseases and insect pests, such as chinch bugs.
Growth Patterns and Turf Maintenance
Turfgrasses employ two distinct strategies for horizontal expansion, which directly impacts maintenance needs. Bunch-type grasses, which include Perennial Ryegrass and most Fescues, grow vertically from a central point, forming individual tufts or clumps. They spread primarily through the production of new tillers from the crown of the plant.
Since bunch-type grasses do not spread laterally to fill damaged areas, bare spots must be repaired through overseeding. In contrast, spreading grasses produce horizontal stems that colonize ground away from the original shoot. These stems are called rhizomes when they grow underground (Kentucky Bluegrass), or stolons when they creep along the soil surface (St. Augustine grass).
Grasses that use rhizomes or stolons, such as Bermuda and Zoysia, are often called “sod-forming” grasses because they create a dense, interwoven mat. This dense growth enables quick recovery from wear and tear, but the rapid accumulation of dead and living stems can lead to a thick layer of thatch. This buildup necessitates periodic mechanical removal, known as dethatching, to ensure water and nutrients reach the soil.