OregonFlora: Poa bulbosa

	Poa bulbosa
	bulbous bluegrass
Habit	Plants perennial but often appearing annual, producing bulblets, 15–60 cm tall, green; cespitose.
Culms	bulbous at the base; nodes terete.
Basal branching	intravaginal.
Leaves	sheaths closed about 25% of their length; basal sheaths swollen at the base; ligules 1–3 mm; blades flat, 1–2.5 mm wide; soon withering.
Inflorescences	ovoid, 3–12 cm; branches 2–5 per node, ascending to spreading.
Spikelets	3–5 mm; florets 3–7, commonly all or all but the lowest producing bulblets, occasionally all producing seeds.
Glumes	keels scabrous; lower glumes 3-veined; upper glumes shorter than or subequal to lowest lemma.
Calluses	with cobwebby hairs or glabrous.
Lemmas	lanceolate, 3–4 mm, distinctly keeled, glabrous throughout, or keels and marginal veins shortto long-villous; area between veins glabrous or softly puberulent; tips acute.
Anthers	developed and 1.4–2 mm, or aborted late in development, or not developed.
2n	=21–42.

	Poa bulbosa
Distribution	[WildflowerSearch map] [BONAP county map]
Discussion	Sunny to partly shady disturbed grasslands, shrub steppe, roadsides. 0–2300 m. All ecoregions except Est. CA, ID, NV, WA; throughout US; Mexico; temperate regions worldwide. Exotic. Poa bulbosa is usually recognized by the bulblets produced in the inflorescence. Occasional non-bulblet-producing plants can be recognized by their bulb-like shoot bases and the presence of bulb-bearing individuals nearby. Some botanists recognize two subspecies, P. b. ssp. bulbosa producing only normal caryopses and P. b. ssp. vivipara, producing bulblets. In Oregon, populations either are entirely viviparous or include both viviparous and seed-producing plants.
Source	Flora of Oregon, volume 1, page 454 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa	P. alpina, P. annua, P. bolanderi, 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
Synonyms	Poa bulbosa ssp. bulbosa, Poa bulbosa ssp. vivipara
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 bulbosa

bulbous bluegrass

Habit

Plants perennial but often appearing annual, producing bulblets, 15–60 cm tall, green; cespitose.

Culms

bulbous at the base;

nodes terete.

Basal branching

intravaginal.

Leaves

sheaths closed about 25% of their length;

basal sheaths swollen at the base;

ligules 1–3 mm;

blades flat, 1–2.5 mm wide; soon withering.

Inflorescences

ovoid, 3–12 cm;

branches 2–5 per node, ascending to spreading.

Spikelets

3–5 mm;

florets 3–7, commonly all or all but the lowest producing bulblets, occasionally all producing seeds.

Glumes

keels scabrous;

lower glumes 3-veined;

upper glumes shorter than or subequal to lowest lemma.

Calluses

with cobwebby hairs or glabrous.

Lemmas

lanceolate, 3–4 mm, distinctly keeled, glabrous throughout, or keels and marginal veins shortto long-villous; area between veins glabrous or softly puberulent;

tips acute.

Anthers

developed and 1.4–2 mm, or aborted late in development, or not developed.

=21–42.

Poa bulbosa

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Sunny to partly shady disturbed grasslands, shrub steppe, roadsides. 0–2300 m. All ecoregions except Est. CA, ID, NV, WA; throughout US; Mexico; temperate regions worldwide. Exotic.

Poa bulbosa is usually recognized by the bulblets produced in the inflorescence. Occasional non-bulblet-producing plants can be recognized by their bulb-like shoot bases and the presence of bulb-bearing individuals nearby. Some botanists recognize two subspecies, P. b. ssp. bulbosa producing only normal caryopses and P. b. ssp. vivipara, producing bulblets. In Oregon, populations either are entirely viviparous or include both viviparous and seed-producing plants.

Source

Flora of Oregon, volume 1, page 454
Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa