Poa annua L.

Global description

Poa annua is a small annual herb, glabrous, 5 to 30 cm high, with numerous stems, ascending prostrate. The leaves with folded aestivation, are flat and smooth, with a single vein, terminating in hook. The ligule is short and truncate. The inflorescence is a short triangular panicle, loose, almost unilateral, carrying a small number of ovoid spikelet, with 3 to 7 fertile flowers. The grain is elongated, trigonal.
 
First leaves
 
The prefoliation is folded. The first 2 leaves are short and narrow (10 to 20 mm long and 0.7 to 1.5 mm wide), folded, keeled. The sheath is flattened, green to light brown in color. The membranous ligule is short (up to 1 mm high), truncate, whitish in color.
 
General habit
 
Annual herb, glabrous, small, measuring 5 to 30 cm high.
 
Underground system
 
The roots are fibrous.
 
Culm
 
The culms are numerous, prostrate ascending, slightly compressed and smooth.
 
Leaf
 
The aestivation is folded. The sheath is smooth. The ligule is membranous truncate and short. The lamina is smooth and glabrous, 3 to 10 cm long and 1.5 to 4 mm wide, completed in hook (the ends of two edges of the blade fused). The leaf blade is flat, soft, a little rough, with only the midrib visible.
 
Inflorescence
 
The inflorescence is an erect panicle, widely triangular, loose, almost unilateral, 3 to 10 cm long and 3 to 5 cm wide. It consists of a central axis and 2 to 3 fine lateral branches, with a small group of spikelets at the tip. The total number of spikelet is 3 to 10.
 
Spikelet
 
The spikelets are flattened ovoid, shortly pedicelled, 3 to 5 mm long and 1.8 to 2.5 mm wide. They are composed of 3 to 7 fertile flowers. The glumes, uneven, barely reach half of the spikelet. They are lanceolate, subacute, and glabrous. The lower glume is uninervate. The lemmas are obtuse, marked with five fairly distinct ribs, pubescent on the back and lateral ribs. The lower lemmas measure 2.8 to 3.7 mm long and 0.7 to 0.9 mm wide. The upper lemmas, smaller in size, is ciliated on the keel. The stamens have yellow anthers.
 
Grain
 
The grain is oblong, trigonal, 1.2 to 1.5 mm long. One of faces slightly depressed, is marked with a small elliptical scar.
 

Origin

Poa annua is native to the Mediterranean basin, Europe and Asia.

Worldwide distribution

This species is now present on all continents but absent from Brazil, tropical Africa and India.

Algeria: Species that has become subcosmopolitan, common in the whole north of the country from the Saharan Atlas.

https://www.gbif.org/fr/species/2704179