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annual bluegrass

Pringle's bluegrass

Habit Plants annual, rarely biennial, 2–20(45)cm tall; cespitose. Plants perennial, dioecious, 5–35 cm tall; densely cespitose.
Culms

nodes terete or weakly compressed.

0.5–0.9 mm thick;

nodes 0(1) exserted.

Basal branching

intravaginal.

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.

sheaths terete, closed to 33% of their length, bases of basal sheaths glabrous, collar margins smooth or scabrous to hispidulous;

ligules (0.5)1–6 mm long, translucent;

tips truncate to acute, ligules of sterile shoots 1–2.5 mm long;

blades involute, frequently somewhat arcuate, 1.5–3 mm wide;

lower surfaces smooth;

upper surfaces densely scabrous or hispidulous;

cauline blades only slightly reduced higher on the culm.

Inflorescences

1–7(10)cm;

branches ascending to spreading or reflexed.

erect, narrowly lanceoloid to ovoid, moderately congested, 1–6 cm;

spikelets 6–20(25);

branches erect, 0.5–1.5(2)cm, 1–2 per node, with 1–3 spikelets.

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.

broadly lanceolate; to 3.5 times as long as wide, 6–8(12) mm; shiny;

florets 2–5;

rachilla internodes smooth.

Glumes

lower glumes smooth, 1-veined.

lanceolate to broadly lanceolate, 3.5–7.5 mm, those of male plants shorter and with rounder tips than those of female plants; thin; shiny; almost transparent;

keels smooth or sparsely scabrous;

lower glumes slightly shorter than adjacent lemma, 3-veined.

Calluses

glabrous.

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.

lanceolate, 5–8 mm, thinly membranous, distinctly keeled; smooth or sparsely finely scabrous, glabrous;

tips acute.

Anthers

0.6–1.1 mm, oblong.

vestigial and 0.1–0.2 mm on female plants, 2–4 mm on male plants.

2n

=28.

Poa annua

Poa pringlei

Distribution
[WildflowerSearch map]
[BONAP county 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.

Rocky, subalpine and alpine slopes. 1200–2300m. Sisk. CA. Native.

Poa pringlei is a dioecious grass with relatively long, nearly transparent glumes. It is cespitose, but the culms spread horizontally at the base, making it appear rhizomatous.

Source Flora of Oregon, volume 1, page 453
Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting
Flora of Oregon, volume 1, page 464
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
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. reflexa, P. rhizomata, P. secunda, P. stenantha, P. suksdorfii, P. trivialis, P. unilateralis, P. wallowensis, P. wheeleri
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