How to Grow Kentucky Bluegrass

Where Kentucky bluegrass grows best

Penn State calls Kentucky bluegrass the most important lawn grass in the United States, and its home ground is the north-central and northeastern states. Penn State says it is best adapted where the average July temperature stays at or below 75°F. Summer heat is what limits it everywhere else.

That makes the transition zone tricky. K-State says bluegrass handles heat less well than tall fescue or the warm-season grasses and does comparatively poorly in Kansas summers. University of Kentucky turf specialists go further: despite the state’s nickname, they rate tall fescue as the best-adapted lawn grass for Kentucky and say bluegrass takes more work and money to keep looking good there. In Texas, Texas A&M considers it adapted only in the Panhandle, with irrigation. UC IPM reports poor summer performance in the hot inland parts of California. In Florida it shows up only as a temporary winter overseed, and UF/IFAS prefers ryegrass for that job.

Give it well-drained, fertile soil with a pH between 6.0 and 7.0, says K-State. It does poorly on shallow or compacted soils.

Seed or sod

Bluegrass can be seeded or sodded. Seed is cheaper but slow: expect sprouts in about two to four weeks, then several more weeks before the lawn fills in. Once it does, the rhizomes spread sideways and fill thin or worn spots, something bunch-type tall fescue and perennial ryegrass cannot do.

Kentucky bluegrass is the most common cool-season sod grass in Pennsylvania, according to Penn State, because the rhizomes knit the sod together. Sod can go down almost any time the ground is not frozen. K-State says your odds are best in September or October. Spring sod has less root under it by summer and needs careful watering through dry spells, and summer-laid sod suffers the most from heat and drought.

When to seed Kentucky bluegrass

Late summer to early fall is the best window. The dates for your zone above follow that rule: from about six weeks to four weeks before your average first fall frost. Kansas seeds in September (K-State); Indiana and Nebraska from mid-August to mid-September. Illinois wants at least 45 days before the first frost, so aim for the early side, because bluegrass is slow to get going. Fall seedings face warm soil, mild air and few weeds, and Penn State points out they get two cool seasons to establish before summer.

Spring is second best. Purdue says to seed as early as possible, while K-State suggests late March or April and Kentucky mid-February to mid-March, no later than mid-April. Crabgrass is the main threat. K-State says siduron is the only preemergence herbicide that is safe at bluegrass seeding time; Kentucky also lists mesotrione.

Bluegrass has one useful quirk. Maryland notes that unsprouted bluegrass seed can survive the winter, while the seed of other lawn grasses dies. Purdue uses this for dormant seeding, sowing between Thanksgiving and March in Indiana so the seed sprouts as the soil warms in April or May.

Seeding rate and choosing seed

Sow 2-3 lb per 1,000 sq ft for a new lawn, and about half that when overseeding (Nebraska). Spread half the seed in one direction and half crosswise, then rake lightly so most seed is covered by about ¼ inch of soil (Penn State).

Buy a blend of three or four cultivars. Penn State explains that each bluegrass cultivar has little genetic variation, so blending improves disease resistance and adaptability. Nebraska advises against seed labeled “variety not stated” and against the old cultivar Kenblue. Mixing species also helps: Penn State’s sunny-lawn mix is 80-90% bluegrass and 10-20% perennial ryegrass, and UC IPM recommends at least 15% ryegrass in California.

Watering a new seeding

Keep the seedbed constantly moist until it sprouts. Nebraska suggests watering two to four times a day for the first two weeks, keeping the top ½ to 1 inch of soil damp. As seedlings approach mowing height, cut back to two or three deeper waterings a week to push roots down. In a mix, Maryland says to wait for the slowest grass, which is the bluegrass, before you cut back. Purdue starts mowing new bluegrass at 1.5 inches once blades reach about 2 inches, then raises the mower to its normal height after three or four mowings.

Mowing, watering and feeding an established lawn

Sources differ on height: K-State recommends 2-3 inches, Purdue 2.5-3.5 inches, and UC IPM 1.5-2.5 inches for California. Remove no more than one-third of the blade at a time. Mowing high grows deeper roots and better heat and drought tolerance, and mowing too low invites weeds. Utah State lowers the last mowing of the year to about 1.5 inches to reduce winter disease.

Bluegrass needs more water than most Kansas lawn grasses. K-State says it takes about 1.5 inches a week in hot weather to stay green. Water in the morning and soak the soil 6-8 inches deep. Water when the grass takes on a bluish cast or footprints linger. Without water it goes dormant and brown but usually survives. UC IPM’s California advice is different because bluegrass roots stay shallow there: water every one to three days in summer.

Do most of your fertilizing in fall. K-State warns that feeding in March or early April forces leaf growth and drains the stored carbohydrates the roots need. K-State’s rough guide is 1-2 lb of nitrogen per 1,000 sq ft a year for a low-input lawn and 4-5 lb for a high-input, irrigated one.

Common problems

• Summer stress. Heat and drought push it into dormancy, especially in the transition zone and hot inland areas.
• Weeds in slow seedings. Slow germination gives weeds time to move in, which is one more reason to seed in fall.
• Crabgrass in spring seedings. Only seeding-safe preemergence products (siduron; Kentucky also lists mesotrione) can go down at planting.
• Disease and insects. UC IPM says bluegrass is susceptible to most turfgrass diseases and insects when stressed. Tennessee notes many varieties are especially prone to red thread, and that bluegrass billbug larvae cause straw-colored patches from late June to early August.
• Thatch. Penn State notes that turf-type cultivars need dethatching to stay productive.