Annual bluegrass (Annual meadow grass, Winter grass)
Poa annua

P. annua is an annual grass, which may persist as a short-lived perennial depending on habitat, climate and management. It is a weakly competitive weed with rapid flowering and profuse seedling.

Leaves are often transversely wrinkled with characteristic tramlines.

Tufted, 5 - 30 cm (1.97 - 11.81 inch) high, root at the nodes, youngest leaf folded.

Erect, in the vegetative state geniculate. Flowering culms are erect and smooth 10 - 30 cm (3.93 - 11.81 inch) tall, without hairs.

Leaves flat, slightly keeled with characteristic 'tramlines'; smooth and abruptly contracted at the apices ('boat-shaped tip'). Transversely wrinkled.
Ligule membranous and typically 2-3(-5) mm 0.078 - 0.118 - 0.197 inch) long, often truncate or acute.
No auricles.
Sheath is smooth, keeled and somewhat compressed.