OregonFlora: Poa annua

	Poa annua
	annual bluegrass
Habit	Plants annual, rarely biennial, 2–20(45)cm tall; cespitose.
Culms	nodes terete or weakly compressed.
Basal branching	intravaginal.
Leaves	sheaths closed about 33% of their length; ligules 0.5–3(5) mm; blades flat or weakly folded, 1–10 cm × 1–3(6)mm; smooth.
Inflorescences	1–7(10)cm; branches ascending to spreading or reflexed.
Spikelets	3–5 mm long; florets 2–6; rachilla internodes smooth, glabrous; more or less concealed, occasionally exposed; distal rachilla internode less than 50(75)% of the length of distal lemma.
Glumes	lower glumes smooth, 1-veined.
Calluses	glabrous.
Lemmas	lanceolate, 2.5–4 mm, keeled; smooth; keels; marginal veins; and usually intermediate veins crisply puberulent to long-villous, rarely glabrous; area between veins glabrous; tips obtuse to acute.
Anthers	0.6–1.1 mm, oblong.
2n	=28.

	Poa annua
Distribution	[WildflowerSearch map] [BONAP county map]
Discussion	Disturbed areas, parking lots, lawns, shores. 0–1700m. BR, BW, Casc, Col, CR, Est, Lava, Sisk, WV. CA, ID, NV, WA; throughout southern Canada and US; worldwide. Exotic. Poa annua is a small but abundant annual with spreading inflorescence branches and oblong anthers. Poa infirma is very similar but has ascending inflorescence branches and shorter, nearly spherical anthers. Poa supina, supine bluegrass, has inflorescences similar to P. annua, but it is a stoloniferous perennial with longer anthers. It is planted on shady golf courses and lawns where it forms dense, spongy turf. It has not been found in the wild in Oregon but is expected to escape here.
Source	Flora of Oregon, volume 1, page 453 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	P. alpina, P. bolanderi, P. bulbosa, P. chambersii, P. compressa, P. confinis, P. cusickii, P. fendleriana, P. glauca, P. howellii, P. iconia, P. infirma, P. laxiflora, P. leibergii, P. leptocoma, P. lettermanii, P. macrantha, P. mansfieldii, P. marcida, P. nemoralis, P. nervosa, P. palustris, P. piperi, P. pratensis, P. pringlei, P. reflexa, P. rhizomata, P. secunda, P. stenantha, P. suksdorfii, P. trivialis, P. unilateralis, P. wallowensis, P. wheeleri
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Poa annua

annual bluegrass

Habit

Plants annual, rarely biennial, 2–20(45)cm tall; cespitose.

Culms

nodes terete or weakly compressed.

Basal branching

intravaginal.

Leaves

sheaths closed about 33% of their length;

ligules 0.5–3(5) mm;

blades flat or weakly folded, 1–10 cm × 1–3(6)mm; smooth.

Inflorescences

1–7(10)cm;

branches ascending to spreading or reflexed.

Spikelets

3–5 mm long;

florets 2–6;

rachilla internodes smooth, glabrous; more or less concealed, occasionally exposed;

distal rachilla internode less than 50(75)% of the length of distal lemma.

Glumes

lower glumes smooth, 1-veined.

Calluses

glabrous.

Lemmas

lanceolate, 2.5–4 mm, keeled; smooth; keels; marginal veins; and usually intermediate veins crisply puberulent to long-villous, rarely glabrous; area between veins glabrous;

tips obtuse to acute.

Anthers

0.6–1.1 mm, oblong.

=28.

Poa annua

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Disturbed areas, parking lots, lawns, shores. 0–1700m. BR, BW, Casc, Col, CR, Est, Lava, Sisk, WV. CA, ID, NV, WA; throughout southern Canada and US; worldwide. Exotic.

Poa annua is a small but abundant annual with spreading inflorescence branches and oblong anthers. Poa infirma is very similar but has ascending inflorescence branches and shorter, nearly spherical anthers. Poa supina, supine bluegrass, has inflorescences similar to P. annua, but it is a stoloniferous perennial with longer anthers. It is planted on shady golf courses and lawns where it forms dense, spongy turf. It has not been found in the wild in Oregon but is expected to escape here.

Source

Flora of Oregon, volume 1, page 453
Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa