Kentucky Bluegrass
by Cameron Hoffer
Kentucky bluegrass is native to almost all of Europe, northern Asia, Algeria and Morocco. Although the species is spread over all of the cool, humid parts of the U.S., it is not native to this part of the world. It was probably brought here by early colonists.
Varieties Over 100 cultivars of Kentucky bluegrass have been developed in the last quarter century. Some varieties tolerate warmer temperatures better than others, some have moderate shade tolerance and some can withstand closer mowing. Select a blend of about 3 varieties for planting to increase your opportunity for good growth. Many of these grasses differ in their degree of susceptibility to leaf spot diseases and Fusarium blight. A blend of several varieties will usually appear superior to a single variety since all varieties are usually not affected by all negative conditions, at least not at the same time.
Propagation
It is best to plant 2 to 3 pounds per 1,000 sq. ft. of lawn. Lower seeding rates require longer to develop a cover, particularly where seed are spread over the soil surface. Where seeds are drilled into the top inch of soil, not as much seed is needed. Kentucky bluegrass can be seeded all year, but best results are obtained in the spring and autumn. New seedings require light, and frequent watering (2 to 3 times per day for the first 2 weeks). After seedlings emerge, watering frequency can be lessened.
Management
Mowing can start when it grows above about a 2-inch cutting height. The first cutting should be at a 2-inch height. Subsequent mowings should be often enough so that no more than one-third of the leaf is removed at each mowing. Weekly mowing is usually OK at the 2-inch mowing height. At lower mowing heights more frequent mowing is needed. Some of the improved bluegrass varieties such as Fylking, Ram I and Touchdown tolerate mowing heights below 1 inch. However, weaker stands of Kentucky bluegrass result when mowing height is less than 1 inch. Also, at mowing
heights below 1 inch invasives such as annual bluegrass and crabgrass are a problem. Also att heights above 1 inch weeds are much less of a problem.
Kentucky bluegrass has a high water requirement. As much as 2 inches of water per week are required to sustain bluegrass's dark color. Ideally this amount of water would be applied in one 24 hour period to wet the entire rootzone. But, the effective rootzone is often not deep enough to hold that amount of water. No less than 1 inch of water should be applied on any single day to increase root depth.
Where bluegrass is allowed to go dormant during drought periods, as little as 1 inch of water every 2 to 3 weeks will keep the grass alive. Then, after water is placed the grass will quickly recover. The drought resistance of Kentucky bluegrass is generally underestimated; it can survive several months without significant amounts of water.
Nitrogen needed by Kentucky bluegrass is much higher during the initial year than during subsequent years. The grass will respond to 5 to 6 pounds of N the first year. However, only 2 to 3 pounds are needed for maintenance after the establishment year. During summer months Kentucky bluegrass will burn if too much soluble nitrogen is applied at one time or if it is not watered in immediately after application. No more than 1 pound of soluble nitrogen per 1,000 sq. ft. should be applied per application. Slow release nitrogen sources can be applied in larger amounts and less often.
Weed, Pest and Disease Management
Annual bluegrass, crabgrass, dandelions and clover are big time weed problems in Kentucky bluegrass turf. The annual grasses can be controlled with timely applications of preemergence herbicides. The broadleaf weeds are well controlled with hormone type herbicides.
Insects like white grubs, billbugs and sod webworms can destroy plantings of bluegrass. Insects should be monitored so that timely insecticide applications can be applied.
Major diseases of bluegrass turf include Fusarium, Helminthosporium leaf spot diseases, rust and powdery mildew. Using cultivars of bluegrass with different levels of resistance to these diseases is one way to control them. Overseeding bluegrass turf with perennial ryegrass or planting mixtures of bluegrass and ryegrass provides a good control of Fusarium blight.
References
Picture
http://www.bluegrasses.com/info/midnight.html
Contact Cameron Hoffer