Kentucky Bluegrass

Kentucky Bluegrass is one of the most predominant cool-season grasses in the United States. Its dark green color, dense growth, and fine to medium leaf blades make for a classic looking lawn. However, it requires more maintenance to maintain a healthy and green lawn. Therefore, Kentucky bluegrass is often mixed with tall fescue in sod production which provides advantages in pest and stress tolerance while maintaining a uniform appearance. 

Is Kentucky bluegrass right for my lawn?

Kentucky bluegrass thrives in cooler and more humid environments and therefore is more prevalent in the northern half of the country. It grows actively in late summer to early winter, and then again in spring to early summer. It struggles during the heat and drought of the summer months. It prefers full sun.

A Kentucky bluegrass lawn requires a commitment to maintenance, requiring more care than some other species. In addition to greater water and nutrient needs, it can also produce a significant thatch layer and annual aerating may be needed.

Establishing a Kentucky bluegrass lawn

For best results, a soil test should be conducted prior to planting a Kentucky bluegrass lawn to determine the nutrient and liming needs. If the soil test results call for a large amount of nutrients, they should be incorporated into the seedbed prior to seeding. In addition, Kentucky bluegrass prefers soils in the pH range of 6 and 7, and liming may be recommended.

Kentucky bluegrass can be seeded or sodded. Newer varieties of Kentucky bluegrass have been bred for better resistance to diseases and are recommended.  Like other cool-season grasses, Kentucky bluegrass is best seeded in late summer as early spring seedings are prone to damage from weeds and summer drought. Kentucky bluegrass should be seeded at a rate of 2 to 3 lbs /1,000 square feet. Slightly slower to establish than many other cool-season grasses, seeds take approximately 2 weeks to germinate. However, once established, Kentucky bluegrass spreads quickly laterally underground. Sod can be installed throughout the year, except when the ground is frozen or in summer when extreme heat or drought is forecast.

New lawns have a greater irrigation need than established lawns and therefore it is important to irrigate frequently, but lightly until a viable root system takes hold.

Caring for your Kentucky bluegrass lawn

Fertilization: Kentucky bluegrass has a high nutrient level requirement. If under-fertilized, it tends to get many of the nuisance turf diseases of dollar spot, red thread, and rust. Leaving grass clippings can help to meet some of the lawn’s fertilization needs, unless the clippings are too thick, in which case they should be collected and composted elsewhere.

Mowing: Mow Kentucky bluegrass from to 2 to 3 ½” in the spring and fall; in the summer, the grass can be allowed to grow taller, but never more than 5”.

Watering: Established lawns need about 1 to 1 ¼” of water every week to maintain green color, preferably delivered all at once. Lawns with sandy soils require more frequent watering to maintain color, though maintain the amount at 1 ¼”. Dark bluish gray grass and wilted, folded, or curled leaves can be used as a visual indication that it is time to water.  Though not recommend, if the lawn is allowed to go dormant during the hottest months, it should be lightly watered at least every 3 weeks to keep the lawn alive until cooler weather arrives.

Pests: White grubs, billbugs and sod webworms can destroy plantings of bluegrass. Therefore, monitoring for these species should be conducted in order to address the issue before lawn damage occurs.

Diseases: Kentucky bluegrass is highly susceptible to summer patch during summer conditions of heat and drought stress, and is most severe in soils that are poorly drained, as moist soils promote disease development.  Other diseases of Kentucky bluegrass include other fungal infections such as brown patch, leaf spot, rust and powdery mildew.

Weeds: Because of the density of Kentucky bluegrass lawns, they typically do not have extensive weed issues. Bluegrass lawns that have thinned out will have a poor ability to out-compete weeds; a regular reseeding regime with improved varieties can help fill in these areas to keep the weeds out.