Kentucky Bluegrass (Poa pratensis) — identification, habitat & look-alikes

Kentucky bluegrass is the classic cool-season lawn grass of the northern US, but it is not originally from Kentucky: it is native to Europe and northern Asia, and whether any North American populations are native is still debated. Left unmowed, it grows 2–3 ft (60–90 cm) tall, and its flower heads take on a bluish look, which gave it its name. On the northern Great Plains it has spread into native prairie and become a serious invader.

Appearance

Growth form: A perennial grass usually 1–2.5 ft (30–70 cm) tall, with flowering stems reaching about 3 ft (90 cm). It spreads by underground runners (rhizomes) to form a dense sod.
Leaves: Narrow, dark blue-green leaves up to 8 in (20 cm) long with boat-shaped tips.
Flowers: An open, pyramid-shaped flower cluster with small purplish-green or gray spikelets.
Flowering time: May–July

Look-alikes

Annual bluegrassPoa annua

Annual bluegrass is light green, grows in small clumps without rhizomes, and keeps producing seed heads from April to October even when mowed very short. Kentucky bluegrass is darker and spreads by rhizomes.

Why they get mixed upBoth have boat-shaped leaf tips and show up in the same lawns.

Rough bluegrassPoa trivialis

Rough bluegrass spreads by aboveground runners (stolons) instead of rhizomes and has a long, pointed, papery collar flap (ligule) about 0.2 in (4–6 mm) long. Kentucky bluegrass has a short, even ligule.

Why they get mixed upIts leaves also have boat-shaped tips, and it is sometimes planted in shady lawns.

Tall fescueLolium arundinaceum

Tall fescue has sharp-pointed leaf tips, deep ridges along the upper leaf surface, and rough edges, and it grows in clumps rather than spreading by rhizomes. Kentucky bluegrass has boat-shaped tips and spreads into a sod.

Why they get mixed upBoth are common cool-season lawn grasses and are often grown together.

Where it lives

Typical habitats: lawns and parks
pastures
roadsides
prairies and meadows
Range: Found across the US and Canada, in lawns and pastures as well as roadsides and wild grasslands.
Preferred conditions: Thrives in fertile, well-drained soil and cool, humid climates. It suffers in summer heat and drought.

Growing it

Care: Widely used for home lawns, parks, and sports fields, including NFL and MLB playing surfaces, often in blends. Since the 1950s, about 90% of US seed has been grown in Idaho, Oregon, and Washington.
Propagation: Spreads by seed and by creeping rhizomes.

Name and classification

Varieties and forms: Many turf cultivars exist, bred for color, density, and heat or disease tolerance. Breeders have also crossed it with Texas bluegrass for better drought and heat tolerance.

Conservation

IUCN Red List: LCLeast ConcernLow risk of extinction
Threats: On the northern Great Plains, especially in North and South Dakota, it has quickly come to dominate many untilled native prairies, crowding out native plants. It is also a common weedy invader in cool, moist areas such as the Pacific Northwest and the Northeast.