OregonFlora: Poa cuspidata vs. Poa infirma

	Poa cuspidata	Poa infirma
		weak bluegrass
Habit		Plants annual, 2–15 cm tall; cespitose.
Culms		nodes terete.
Basal branching		intravaginal.
Leaves		sheaths closed about 33% of their length; ligules 0.5–3 mm; blades flat, 1–3(4) mm wide; smooth.
Inflorescences		1–6 cm; branches ascending; spikelets crowded.
Spikelets		3–5 mm; florets 2–6; rachilla internodes smooth, glabrous, usually exposed in side view; distal internode 50–75% the length of the distal lemma.
Glumes		smooth; lower glumes 1-veined.
Calluses		glabrous.
Lemmas		lanceolate, 2–2.5 mm, distinctly keeled; smooth throughout; keels; marginal and intermediate veins crisply puberulent to long-villous; area between veins glabrous, intermediate veins prominent; tips obtuse to acute.
Anthers		0.1–0.5(0.6)mm; spherical to short-elliptical.
2n		=14.

	Poa cuspidata	Poa infirma
Distribution	[WildflowerSearch map] [BONAP county map]	[BONAP county map]
Discussion		Disturbed areas, gravel parking areas, railroads. 50–1100m. WV. CA; British Columbia, SC; South America; Europe. Exotic. Poa infirma is a small annual bluegrass very similar to P. annua but with ascending inflorescence branches and smaller, nearly spherical anthers. It has been collected rarely in Oregon.
Source		Flora of Oregon, volume 1, page 458 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	P. alpina, P. annua, 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	P. alpina, P. annua, P. bolanderi, P. bulbosa, P. chambersii, P. compressa, P. confinis, P. cusickii, P. fendleriana, P. glauca, P. howellii, P. iconia, 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 Web sites: 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	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 cuspidata

Poa infirma

weak bluegrass

Habit

Plants annual, 2–15 cm tall; cespitose.

Culms

nodes terete.

Basal branching

intravaginal.

Leaves

sheaths closed about 33% of their length;

ligules 0.5–3 mm;

blades flat, 1–3(4) mm wide; smooth.

Inflorescences

1–6 cm;

branches ascending;

spikelets crowded.

Spikelets

3–5 mm;

florets 2–6;

rachilla internodes smooth, glabrous, usually exposed in side view;

distal internode 50–75% the length of the distal lemma.

Glumes

smooth;

lower glumes 1-veined.

Calluses

glabrous.

Lemmas

lanceolate, 2–2.5 mm, distinctly keeled; smooth throughout; keels; marginal and intermediate veins crisply puberulent to long-villous; area between veins glabrous, intermediate veins prominent;

tips obtuse to acute.

Anthers

0.1–0.5(0.6)mm; spherical to short-elliptical.

=14.

Poa cuspidata

Poa infirma

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Disturbed areas, gravel parking areas, railroads. 50–1100m. WV. CA; British Columbia, SC; South America; Europe. Exotic.

Poa infirma is a small annual bluegrass very similar to P. annua but with ascending inflorescence branches and smaller, nearly spherical anthers. It has been collected rarely in Oregon.

Source

Flora of Oregon, volume 1, page 458
Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa