Kentucky Bluegrass
LawnBluegrass, Poa pratensis, Common Bluegrass
Cool-season grass dominant in zones 3–7. Dormancy: goes dormant (tan/brown) when temps exceed 32°C for 2+ weeks, or when drought-stressed. Recovery: greens up rapidly in cool, moist conditions. Overseeding window: early fall (soil 50–65°F). Spring green-up: consistent temps >10°C for 14 days. Mow at 2.5–4 in (never remove more than 1/3 at once). Summer stress protocol: raise mowing height to 4 in; water deeply 1x/week (1 in); allow partial dormancy in severe heat rather than forcing growth. Fall prep: aerate + overseed + fertilize (Oct in zone 5–6, Sep in zone 4). Fertilize schedule: heavy fall feed (1 lb N/1000 sqft), light spring feed to avoid disease. Spreads by rhizomes — self-repairs bare spots over time.
When to sow Kentucky bluegrass
Sow 6–8 weeks before your first autumn frost.
Dashed line: typical first autumn frost in zone 7 (Nov 1). Zone dates are averages; most of the UK is zone 8–9, central Europe 6–7 and the Baltics and Scandinavia 4–6. In the app, Tomatograph uses your garden's own frost dates.
How to establish and care for Kentucky bluegrass
- 1
Sow in early autumn
Sow or overseed in early autumn when the soil is 10–18 °C. It is a cool-season grass suited to cold winters.
- 2
Mow high
Mow at 6–10 cm and never remove more than a third of the blade at once. Raise the height to 10 cm in summer heat.
- 3
Water deeply
Water deeply about once a week, around 2.5 cm, rather than little and often. In a long heatwave above 32 °C it may go brown and dormant, then recover in cool, moist weather.
- 4
Feed in autumn
Give the main feed in autumn and only a light one in spring to avoid disease. It spreads by rhizomes and fills bare patches on its own over time.
Growing conditions
Light
Full sun
Water
High water
Temperature
-30–29 °C
Frost tolerance
Frost-hardy — tolerates frost
How Tomatograph watches your Kentucky bluegrass
Tomatograph checks your local forecast every morning and only speaks up when one of these applies to your garden.
- 30 °C or more with under 5 mm of rain forecast over 3 daysDeep-watering reminder before the lawn goes into heat stress.
- 3 nights at 0 °C or below in the forecastDormancy notice: stop regular watering, mowing and feeding until spring green-up.
- 30–60 days before your first frostAutumn prep window: aerate, overseed bare patches and apply a slow-release feed.
- Over 20 mm of rain forecast over 3 daysTells you to skip irrigation until the ground dries out.
Kentucky Bluegrass questions
- When should I sow Kentucky bluegrass?
- Sow 6–8 weeks before your first autumn frost.
Growing guide written by Tomatograph. Zone frost dates are averages from openplantdb (CC0 1.0).