OregonFlora: Poa douglasii vs. Poa palustris

	Poa douglasii	Poa palustris
		fowl bluegrass
Habit		Plants perennial, 25–120 cm tall, loosely to densely cespitose and often stoloniferous; shoots all or most flowering at anthesis, vegetative shoots appearing late in the growing season.
Culms		nodes terete to slightly compressed; proximal nodes often slightly swollen; the uppermost node usually at or above the middle of the culm.
Basal branching		extra- and intravaginal.
Leaves		sheaths closed to 20% of their length, bases of basal sheaths glabrous; ligules (1)1.5– 6 mm, truncate to acute; blades flat, 1.5–8 mm wide, usually several on the culm, steeply ascending or spreading to 80°; upper blades often lax.
Inflorescences		lax, eventually open, sparsely to moderately congested; (9)13–30(41)cm, generally 33–50% as broad as long at maturity; spikelets 25–100+; branches initially erect, eventually widely spreading to slightly reflexed, fairly straight; slender, 4–15 cm, 33–50% of the panicle length, 2–9 per node.
Spikelets		narrowly to broadly lanceolate, 3–3.5 times as long as wide, 3–5 mm; florets (1)2–5; rachilla internodes mostly less than 1 mm.
Glumes		tapering from the base or lanceolate, distinctly keeled; keels smooth or sparsely scabrous; lower glumes 3-veined; long tapered to a slender point, 6.4–10 times as long as wide.

	Poa douglasii	Poa palustris
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Discussion		Moist meadows, shorelines, ditches, forests, disturbed areas. 0–2600m. BR, BW, Casc, Col, ECas, Lava, Owy, WV. CA, ID, NV, WA; throughout most of Canada and US; circumboreal. Exotic? Poa palustris has an open inflorescence, small lemmas and an open growth form produced by culms that often branch above the base. Poa nemoralis differs in having short, truncate ligules. Poa palustris from drier sites can be similar to P. interior, which has more lax leaf blades, calluses with sparse, short hairs, wider hyaline lemma margins and straight to slightly curved lemma keels. Poa interior has not been documented in Oregon. Both native and introduced populations of Poa palustris exist in North America, and Oregon plants have generally be considered introduced. However, some populations may be native.
Source		Flora of Oregon, volume 1, page 461 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. infirma, P. laxiflora, P. leibergii, P. leptocoma, P. lettermanii, P. macrantha, P. mansfieldii, P. marcida, P. nemoralis, P. nervosa, 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: CA 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	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 douglasii

Poa palustris

fowl bluegrass

Habit

Plants perennial, 25–120 cm tall, loosely to densely cespitose and often stoloniferous; shoots all or most flowering at anthesis, vegetative shoots appearing late in the growing season.

Culms

nodes terete to slightly compressed;

proximal nodes often slightly swollen; the uppermost node usually at or above the middle of the culm.

Basal branching

extra- and intravaginal.

Leaves

sheaths closed to 20% of their length, bases of basal sheaths glabrous;

ligules (1)1.5– 6 mm, truncate to acute;

blades flat, 1.5–8 mm wide, usually several on the culm, steeply ascending or spreading to 80°; upper blades often lax.

Inflorescences

lax, eventually open, sparsely to moderately congested; (9)13–30(41)cm, generally 33–50% as broad as long at maturity;

spikelets 25–100+;

branches initially erect, eventually widely spreading to slightly reflexed, fairly straight; slender, 4–15 cm, 33–50% of the panicle length, 2–9 per node.

Spikelets

narrowly to broadly lanceolate, 3–3.5 times as long as wide, 3–5 mm;

florets (1)2–5;

rachilla internodes mostly less than 1 mm.

Glumes

tapering from the base or lanceolate, distinctly keeled;

keels smooth or sparsely scabrous;

lower glumes 3-veined; long tapered to a slender point, 6.4–10 times as long as wide.

Poa douglasii

Poa palustris

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Moist meadows, shorelines, ditches, forests, disturbed areas. 0–2600m. BR, BW, Casc, Col, ECas, Lava, Owy, WV. CA, ID, NV, WA; throughout most of Canada and US; circumboreal. Exotic?

Poa palustris has an open inflorescence, small lemmas and an open growth form produced by culms that often branch above the base. Poa nemoralis differs in having short, truncate ligules. Poa palustris from drier sites can be similar to P. interior, which has more lax leaf blades, calluses with sparse, short hairs, wider hyaline lemma margins and straight to slightly curved lemma keels. Poa interior has not been documented in Oregon. Both native and introduced populations of Poa palustris exist in North America, and Oregon plants have generally be considered introduced. However, some populations may be native.

Source

Flora of Oregon, volume 1, page 461
Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa