Kentucky Bluegrass Lawns
Kentucky bluegrass is a cool-season turfgrass that spreads by underground stems called rhizomes. It is a highly variable species, with cultivars that differ in color, texture, density, vigor, disease resistance and tolerance to close mowing.
Bluegrass is best adapted to well-drained, moist, fertile soils with a pH between 6.0 and 7.0. It does best in full sun but will tolerate light shade. It does not perform well on shallow, compacted soils, or where the pH is excessively high or low. It is not as heat tolerant as tall fescue and the warm-season grasses, so it performs comparatively poorly during Kansas summers.
Good soil preparation is extremely important for a quality Kentucky bluegrass lawn. One of the best ways to improve the soil is by tilling in good quality organic matter (e.g. compost or peat) before planting. Add 3 to 6 cubic yards of organic matter per 1,000 square feet and till it in 8 to 10 inches deep.
Kentucky bluegrass lawns are established by seeding or sodding. September is the best time for seeding bluegrass because soil temperatures are warm, air temperatures are moderating, and weed competition is minimal. Spring seedings (late March or April) are more difficult, but possible. Spring seedings may require crabgrass control with the preemergence herbicide siduron (Tupersan). Siduron is the only preemergence herbicide that can be used at the time of seeding. DCPA (Datchal) can be used when the seedlings are 1 inch tall. No other preemergence or postemergence herbicides should be applied until the new lawn has been mowed at least 3 times.
Kentucky bluegrass should be seeded at a rate of 2 to 3 pounds per 1,000 square feet. Bluegrass is relatively slow in getting started, so be patient. If the seed is kept constantly moist, it will germinate in 14 to 21 days, depending on the soil temperature.
Sodding is possible about any time of the year, although chances for successful establishment are much higher if done in September or October. Lawns sodded in the spring will require more careful irrigation during summer dry spells because their root systems will be less developed than those sodded the previous fall. Summer-sodded lawns will be most susceptible to heat and drought stress.
Kentucky bluegrass generally needs more water to stay green than most other Kansas turfgrasses. It will, however, survive extended hot, dry periods by going dormant if it is not irrigated. If allowed to go dormant, bluegrass can be considered a water-saving grass, but it will be brown in color.
If a green color is desired all summer, bluegrass will require approximately 1½ inches of water per week during hot weather. Less water is needed in the spring and the fall. Morning watering is most efficient and may help prevent some diseases. Soak the lawn thoroughly. The goal is to wet the soil to a depth of 6 to 8 inches. By doing so, the interval between successive waterings is lengthened.
Tip: When the turf begins to turn a bluish cast, or when walking across the lawn leaves lingering footprints, the lawn needs water.
Kentucky bluegrass does best when mowed at a height of 2 to 3 inches. Mowing too low encourages weed invasion. Additionally, root growth is proportional to shoot growth, so mowing high encourages deeper rooting and leads to a more heat- and drought-resistant turf. Mow often enough so that no more than one-third of the foliage is removed at a time. Frequent mowing also makes it not necessary to catch the clippings.
The amount of fertilizer needed depends on expectations for the lawn. A lower-input Kentucky bluegrass lawn, where appearance is not the primary objective, should be fertilized once or twice a year. A high-input lawn, where appearance is a primary objective, will require more fertilizer.
Most of the fertilizer should be applied in the fall. Fertilizing too early in the spring (March or early April) causes excessive growth and can deplete the turf of stored carbohydrates needed for root growth. The result is a weakened turf that is more susceptible to diseases, insects and drought.
Nitrogen is the fertilizer nutrient required in the greatest quantities and the greatest regularity. Nitrogen sources are classified as quick-release or slow-release Many contain a combination of the two types. Spring and summer applications of nitrogen should generally consist of slow-release forms. These promote more controlled growth. An alternative would be to use lighter, more frequent applications of quick-release nitrogen.