What is familiarly known as Kentucky bluegrass is actually one of the most widespread varieties of grasses in the world, with a native range that spreads across most of Asia and Europe. The grass, identifiable by its silvery-blue cast and tips that resemble the prow of a boat, grows best in cooler regions with adequate annual rainfall.
Exactly how Kentucky bluegrass (Poa pratensis) came to the Americas is unclear. The most likely scenario is that the grass arrived with settlers to the New World in the 1600s, probably as part of grass seed and turf mixtures brought along by European settlers. Though Kentucky bluegrass is still considered to be a non-native, introduced species, the grass has become widely naturalized across much of the United States. It grows well beyond the boundaries of Kentucky’s so-called “bluegrass region,” in the state’s north-central reaches.
Care and Culture
Kentucky bluegrass is widely used as both a turfgrass for sporting fields and lawn grass. It grows best under cooler, moister conditions and is rarely found in the states of the deep South or in the arid regions of the western United States. After seeding, Kentucky bluegrass can take two to three years to become well established, after which it forms a very sturdy sod clump through rhizomous growth. Grass may go completely dormant during hot summer months but readily regenerates after temperatures drop and watering resumes. Kentucky bluegrass requires regular applications of fertilizer to maintain healthy growth and color, especially during the spring and autumn months.
Research at Rutgers University has led to over 100 named varieties of hybrid Kentucky bluegrasses, many of which were developed by crossing it with a species of Texas bluegrass (Poa arachnifera). The resulting hybrids displayed increased heat and drought tolerance. Several varieties widely available on the market today include Reveille, Longhorn, Thermal Blue and Solar Green.
Though hybridization has improved the disease resistance of Kentucky bluegrass varieties, major diseases of the grass still include leaf spot, crown rot and patch disease. All of these diseases cause damage and discoloration of the grass blades. Leaf spot and crown rot are more prevalent during extended periods of wet, cloudy weather, while patch disease manifests mainly during hotter, dryer months. Major insect pests of Kentucky bluegrass include white grubs and sod webworms, which are mainly controlled through an annual application of insecticide. These pests damage grass stands by burrowing through and feeding on roots.
Selecting a blend of several different Kentucky bluegrass hybrid cultivars can help with germination and pest problems which can occur when only one strain is used to seed a patch for turf. Newer plantings of Kentucky bluegrass should also generally not be mowed to less than 2 inches, as this weakens the overall stand and makes grass susceptible to invasion by weeds and pests. Watering requirements are higher than for other types of grasses; for optimum growth, color and vigor, Kentucky bluegrass needs as much as 2 inches of water each week to thrive during the hot summer months.