Poa pratensis
Cool-season grassUSDA zones 3–7Dense, dark green turf. The classic American lawn grass. Kentucky Bluegrass is a cool-season grass: it grows most in spring and fall, slows in summer heat, and goes dormant in winter.
| Season | Mowing height |
|---|---|
| Spring | 2.5–3.5 in |
| Summer | 3–4 in |
| Fall | 2–3 in |
With a reel mower, which cuts cleaner and can go lower: 1.5–2.5 inches.
Follow the one-third rule: never remove more than a third of the blade in one cut. At a 4-inch summer height, mow before the lawn passes about 6 inches. In peak spring and fall growth that means about weekly, and less often in summer heat. Raising the deck in summer shades the soil and keeps roots cooler.
| # | When | Nitrogen per 1,000 sq ft | Fertilizer | Notes |
|---|---|---|---|---|
| 1 | Early spring (soil >55F) | 0.5–1 lb | 10-10-10 or 3-1-2 | Light application after the initial spring growth flush ends |
| 2 | Late spring (May) | 0.5–1 lb | 3-1-2 (e.g. 15-5-10) | Optional: skip for minimal maintenance lawns |
| 3 | Early fall (September) | 1 lb | 3-1-2 (e.g. 15-5-10) | Most important application of the year: peak root growth period |
| 4 | Late fall (November, around last mow) | 1 lb | Low-N, high-K (e.g. 10-0-20) | Winterizer with quick-release nitrogen for color and root storage |
The early-fall feeding matters most: it fuels root growth when the grass is recovering from summer. Hold the first spring feeding until the soil has warmed; fertilizer on cold ground mostly washes away. Don't apply more than 1 lb of quick-release nitrogen per 1,000 sq ft at once, and follow a soil test for phosphorus and lime.
Kentucky Bluegrass uses water at about 80% of your area's reference evaporation rate. In summer that usually works out to 1 to 1.5 inches a week from rain and watering combined, less in cool weather. Water deeply and infrequently, once or twice a week before 10 AM, rather than a little every day: deep soaks grow deep roots.
In a long drought, a cool-season lawn can be allowed to go dormant and brown; it recovers when rain returns, but give it about half an inch every two to three weeks to keep the crowns alive.
Pre-emergent crabgrass preventer only works if it's down before the seeds germinate. The most reliable timing is by accumulated warmth: apply between 250 and 500 growing degree days (base 32F) since January 1. How to time crabgrass preventer explains the method and shows when the window opened in five cities in 2026.
Core aerate and overseed in late summer to early fall, about five weeks before your first frost. Warm soil and cooling air make it the best establishment window of the year, and seedlings get the four to six weeks of growth they need before frost. The holes aeration leaves give seed the soil contact it needs.
Past that window, aeration can still run into mid-fall, but save the seed for next year: grass sown within a month of frost usually doesn't survive winter.
Lawn Guardian turns this guidance into a schedule timed to your USDA zone and this week's actual weather — and adapts every time you log what you've done.
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2.5–3.5 inches in spring, 3–4 inches in summer, and 2–3 inches in fall (1.5–2.5 inches with a reel mower). Never remove more than a third of the blade in one cut.
Early spring (soil >55F), late spring (May), early fall (September), and late fall (November, around last mow).
When 250 to 500 growing degree days (base 32F) have built up since January 1, before crabgrass germinates. That ranged from mid-January in Oklahoma City to mid-April in Ottawa in 2026.