On average, cool season areas have cold winters with temperatures that fall below freezing and warm to hot summers.
Usually there are regular intervals of rain throughout the summer months, but grasses will tolerate some extended periods of draught by going dormant, or may require some lawn irrigation to remain green throughout extended periods without rain.
Durable cool-season grasses include the most popular - Kentucky bluegrass, perennial rye, tall and fine fescues. New blends of the turf-type tall fescues are also becoming more widespread.
Textures
Look at the grass' texture to tell it from other types. Coarse tall fescue's big blades and bunching characteristics look rougher than bluegrass and rye's narrow, fine leaves. If your grass has thin, needlelike leaves it is probably a fine fescue.
Colors
Kentucky bluegrass is true green like fine fescue, but turns brown easily during hot weather. Look for new cultivars of tall fescues noted for their reliable dark green even in summer, and perennial ryes that sprout bright green, then darken. See an old lawn with dead patches? Think bent grass, now popular only on golf courses because of its high maintenance requirements.
Growth habits
Rye and tall fescue sprout and take over quickly compared with bluegrass and fine fescue grasses. Most of the older fescues are likely to bunch up and form unsightly clumps over a period of years. However, new varieties of fescue are less likely to do this.
Tall fescue needs little additional irrigation and stands up to regular use as on heavy traffic areas such as a playground. Bluegrass needs regular irrigation to survive extended hot-dry periods and is more sensitive to heavy traffic.
Creeping grasses like bluegrass, Bermuda and most warm season grasses spread by runners, either above or below ground. Creeping grass varieties are more prone to thatch and extra precautions should be taken to avoid thatch build up such as regular aeration treatmentsw.
Bunch grasses such as fescue and ryegrass spread from the crown or central part of the plant. Mowing high protects the crown that is more sensitive to being damaged if cutting is made too close to the cener.