Poa annua L.

Annual Bluegrass


CC = *
CW = 3
MOC = 54

© DETenaglia

Family - Poaceae/Poeae

Habit - Annual grass, without rhizomes, forming tufts.

Stems - Flowering stems 4-30 cm long, spreading to ascending, somewhat flattened, glabrous.

Leaves - Leaf sheaths somewhat keeled, glabrous, open to below the middle, the ligule membranous, 0.8-2.5 mm long, rounded to truncate on the margin. Leaf blades 1-10 cm long, 1-3 mm wide, usually flat, glabrous.

Poa_annua_ligule.jpg Ligule.

© DETenaglia

Inflorescences - Inflorescences 1-8 cm long, open, the lowermost branches single or paired, spreading or loosely ascending.

Poa_annua_inflorescence.jpg Inflorescence.

© DETenaglia

Spikelets - Spikelets 2.5-5.5 mm long, with 2-6 fertile florets. Lower glume 1.5-2.4 mm long, lanceolate, sharply pointed at the tip, with broad, thin margins, faintly 3-nerved, roughened along the midnerve. Upper glume 1.7-2.8 mm long, narrowly ovate, sharply pointed at the tip, with broad, thin margins, 3-nerved, roughened along the midnerve. Lemmas 2.4-3.5 mm long, elliptic, bluntly pointed at the tip, 5-nerved, the lateral nerves all well developed, short-hairy along the nerves but lacking long, cobwebby hairs at the base. Anthers 0.7-1.1 mm long, often exserted from the spikelet at maturity.

Poa_annua_spikelet.jpg Spikelet.

© DETenaglia

Fruits - Caryopses 1.0-1.2 mm long, brownish yellow.

Flowering - January - December.

Habitat - Streambanks, bottomlands, forests, pond margins, pastures, fields, gardens, lawns, roadsides, railroads, disturbed sites.

Origin - Native to Eurasia. Cultivated and escaped nearly worldwide.

Lookalikes - Other grasses.

Other info. - This weedy little species can be found mainly in the southern half of Missouri. The plant can be identified because of its lack of rhizomes (annual habit), big membranous ligules, and lack of hairs. This is a common lawn weed. The species is often spread unknowingly as a contaminant in seed mixes.

Photographs taken off Lee Rd 54, Auburn, AL., 1-20-01 (DETenaglia).