OregonFlora: Poa lettermanii vs. Poa sect. Abbreviatae

	Poa lettermanii	Poa sect. Abbreviatae
	Letterman's bluegrass
Habit	Plants perennial, 1–12 cm tall; densely cespitose.
Basal branching	intra- and extravaginal or mainly intravaginal.
Leaves	sheaths closed to 25% of their length; ligules 1–3 mm; blades flat or folded, or slightly inrolled, 0.5–2 mm wide.
Inflorescences	erect, contracted, 1–3 cm long, usually exserted from the sheaths; branches erect to steeply ascending; slender; to 1.5 cm.
Spikelets	3–4 mm, green or purple; florets 2–3; rachilla internodes less than 1 mm long; smooth.
Glumes	lanceolate to broadly lanceolate, 2.4– 3.6(4) mm, usually equaling or exceeding the lowest lemma, frequently exceeding the upper florets; lower glumes 3-veined.
Calluses	glabrous.
Lemmas	lanceolate, 2.5–3 mm long, distinctly keeled; thin, glabrous; keels and marginal veins rarely sparsely puberulent; tips acute.
Anthers	0.2–0.8 mm.
2n	=14.

	Poa lettermanii	Poa sect. Abbreviatae
Distribution	[WildflowerSearch map] [BONAP county map]
Discussion	Rocky alpine ridges and ledges. 2900–3100m. Casc. CA, ID, NV, WA; north to British Columbia, east to CO. Native. This is a small, cespitose, alpine bluegrass, most similar to P. suksdorfii. Both have subequal glumes that tend to be longer than the lowest lemma, but P. suksdorfii has larger spikelets with longer glumes. In Oregon, P. lettermanii is known only from high elevation on South Sister in the central Cascades.
Source	Flora of Oregon, volume 1, page 459 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. 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	Google search

Poa sect. Abbreviatae

Letterman's bluegrass

Habit

Plants perennial, 1–12 cm tall; densely cespitose.

Basal branching

intra- and extravaginal or mainly intravaginal.

Leaves

sheaths closed to 25% of their length;

ligules 1–3 mm;

blades flat or folded, or slightly inrolled, 0.5–2 mm wide.

Inflorescences

erect, contracted, 1–3 cm long, usually exserted from the sheaths;

branches erect to steeply ascending; slender; to 1.5 cm.

Spikelets

3–4 mm, green or purple;

florets 2–3;

rachilla internodes less than 1 mm long; smooth.

Glumes

lanceolate to broadly lanceolate, 2.4– 3.6(4) mm, usually equaling or exceeding the lowest lemma, frequently exceeding the upper florets;

lower glumes 3-veined.

Calluses

glabrous.

Lemmas

lanceolate, 2.5–3 mm long, distinctly keeled; thin, glabrous;

keels and marginal veins rarely sparsely puberulent;

tips acute.

Anthers

0.2–0.8 mm.

=14.

Poa sect. Abbreviatae

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Rocky alpine ridges and ledges. 2900–3100m. Casc. CA, ID, NV, WA; north to British Columbia, east to CO. Native.

This is a small, cespitose, alpine bluegrass, most similar to P. suksdorfii. Both have subequal glumes that tend to be longer than the lowest lemma, but P. suksdorfii has larger spikelets with longer glumes. In Oregon, P. lettermanii is known only from high elevation on South Sister in the central Cascades.

Source

Flora of Oregon, volume 1, page 459
Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting

Sibling taxa