Grown as lawns throughout the entire northern half of the United States, Kentucky bluegrass (Poa pratensis) is a cool season perennial grass that will grow up to 24 inches tall if not mowed. It produces most of its new shoots in spring and nearly all will remain vegetative throughout the growing season. Shoots produced late in the season often grow a flower stalk the following spring. Kentucky bluegrass is one of the toughest and most vigorously growing grasses and its seeds are often mixed with those of other varieties of grasses when establishing new lawns.
High/Medium Maintenance Varieties
This class of varieties of Kentucky bluegrass have the highest performance level if the turf is adequately maintained. This includes frequent mowing to maintain the desired blade height, adequate and consistent watering, an effective pest and disease management program, and maintaining the turf's fertility with adequate yearly applications of nitrogen fertilizer. Examples of varieties of Kentucky bluegrass in this high to medium maintenance class include Liberator, Chicago, Total Eclipse and Wildwood.
Low Maintenance Varieties
Low maintenance varieties of Kentucky bluegrass have an open, upright growth habit with narrow leaves. They are best used in regions that have cool nights and relatively low humidity. Grow these varieties on sites with limited irrigation infrastructure that can be left to go dormant in summer. Low maintenance varieties of Kentucky bluegrass should be mowed to a height of 2½ inches and only moderately fertilized. Varieties in this class include Barblue, Harmony, Caliber and Monopoly.
The aggressive varieties of Kentucky bluegrass produce dense growth. They are ideal to use for overseeding sparse areas or when initially establishing a stand of grass. These varieties make excellent turf for ball fields and other high-traffic locations. They will produce much more thatch than other Kentucky bluegrass cultivars and will require routine core aerification and de-thatching. Varieties include North Star, Princeton, Touchdown and Limousine.
Compact Kentucky bluegrass varieties have a compact, low growth habit. They can be maintained at a mowing height of only three quarters of an inch as long as they are adequately watered, fertilized and otherwise well-maintained. Two sub-groups exist in this class of varieties: Midnight and America. Those in the Midnight sub-group remain dormant late into spring, but show excellent heat tolerance with dark green blades. The America sub-group produces a high-density turf with a fine leaf texture. However, they show only moderate recovery from summer stress of drought and traffic. Regular compact varieties include Blackstone and Indigo; varieties in the Midnight sub-group are Absolute and Impact; varieties in the America sub-group include Showcase and Unique.
For varieties with good cool weather vigor, choose those in the spring/winter class. These varieties have a medium density and growth habit and green-up early in spring. They are primarily used for sports fields which are needed for early spring sporting events, such as high school baseball or soccer. Two sub-groups in this class are Bellevue types, which tend to grow a lot of stems in late spring and CELA types, which produce less stems. Bellevue varieties include Classic, Freedom or suffolk. CELA types include Challenger, Eclipse and Jefferson.