Poa pratensis L.

Kentucky Bluegrass


CC = *
CW = 3
MOC = 78

© DETenaglia

Family - Poaceae/Poeae

Habit - Perennial cool-season (C3) grass, with well-developed rhizomes, forming clumps or loose colonies.

Stems - Flowering stems 30-100 cm long, erect, circular in crosssection or very slightly flattened, glabrous.

Poa_pratensis_stems.jpg Culms and leaves.

© SRTurner

Leaves - Leaf sheaths rounded or nearly so, glabrous or less commonly somewhat roughened, the ligule 0.7-2.0 mm long, truncate and usually somewhat uneven on the margin. Leaf blades 1-25 cm long, 2-5 mm wide, flat or more commonly folded toward the base, glabrous or roughened along the margins and toward the base.

Poa_pratensis_sheaths.jpg Sheaths.

© SRTurner

Poa_pratensis_ligule.jpg Ligule.

© DETenaglia

Poa_pratensis_leaf.jpg Leaf. The boat-shaped leaf tip is characteristic.

© DETenaglia

Inflorescences - Inflorescences 3-15 cm long, usually open, the lowermost whorled nodes with usually 4 or 5 branches, these spreading or ascending at maturity.

Poa_pratensis_inflorescence1.jpg Inflorescences.

© SRTurner

Spikelets - Spikelets 3-6 mm long, with 3-5 fertile florets. Lower glume 1.7-3.0 mm long, elliptic-lanceolate, sharply pointed at the tip, with broad, thin margins, 1-nerved, roughened along the midnerve. Upper glume 2.2-3.5 mm long, elliptic-ovate, sharply pointed at the tip, with broad, thin margins, 3-nerved, roughened along the midnerve. Lemmas 2.5-4.0 mm long, elliptic, sharply pointed at the tip, 5-nerved, short-hairy along the keel and the outermost pair of lateral nerves, and with a tuft of long, cobwebby hairs at the base. Anthers 1.0-1.5 mm long.

Poa_pratensis_spikelets.jpg Spikelets.

© SRTurner

Poa_pratensis_spikelets2.jpg Spikelets. Though not visible here, a patch of cobwebby hairs is usuall present at the base of the spikelet.

© SRTurner

Fruits - Caryopses 1.5-2.2 mm long, reddish brown, shiny.

Flowering - April - July.

Habitat - Forests, glades, streambanks, pond margins, roadsides, railroads, pastures, fields, lawns, gardens, open disturbed areas.

Origin - Native to Eurasia and possibly also the U.S.

Other info. - This common species can be found throughout Missouri and across the continental U.S. This is the most common grass of lawns and golf courses in the midwestern U.S., and thus the most economically important member of the genus. It is also an excellent forage grass for pastures and hayfields, particularly in areas with calcareous substrate. The pollen is a principal cause of hay fever during May and June. Many varieties and cultivars of this grass have been recognized and/or developed.

The nativity of this grass has been questioned. There is evidence that at least some populations in the northern and western parts of North America are native. Missouri populations are probably all introduced, though the plant has become well naturalized in a variety of habitats.

Photographs taken somewhere in North Carolina, 4-27-03 (DETenaglia); also near Labadie, Franklin County, MO, 4-30-2023 (SRTurner).