OregonFlora: Poa annua vs. Poa secunda

	Poa annua	Poa secunda
	annual bluegrass	secund bluegrass
Habit	Plants annual, rarely biennial, 2–20(45)cm tall; cespitose.	Plants perennial, (10)15–120 cm tall; densely cespitose; basal leaf tufts (excluding culms) 2–20+ cm tall, glaucous or not.
Culms	nodes terete or weakly compressed.	slender to stout; nodes terete, 0–2 exserted.
Basal branching	intravaginal.	intra- and extravaginal.
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 closed to 25% of their length, bases of basal sheaths glabrous; collars smooth or scabrous, glabrous; ligules 0.5–6(10)mm; blades flat, folded, or involute, 0.4–3(5) mm wide, green to strongly glaucous; thin; soft and soon withering, or thick; firm and persisting; smooth, or scabrous mainly over the veins; blades gradually reduced distally or the middle blades longest; uppermost blades 0.8–10(17)cm.
Inflorescences	1–7(10)cm; branches ascending to spreading or reflexed.	erect or somewhat lax, narrowly lanceoloid to ovoid, usually contracted; more or less open in flower, infrequently remaining open at maturity, usually moderately congested, 2–25(30) cm; spikelets 10–100+; branches usually erect or ascending, infrequently spreading at maturity; (0.5)1–8(10) cm, 1–3 per node, with (1)2–20(60+) spikelets in distal 50–67%.
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.	usually narrowly lanceolate; more or less terete to slightly laterally compressed; (3.8)4–5 times as long as wide; (4)5–10 mm; florets (2)3–5(10); rachilla internodes usually 1–2 mm long; smooth to scabrous.
Glumes	lower glumes smooth, 1-veined.	broadly lanceolate; keels indistinct; lower glumes 3-veined.
Calluses	glabrous.	glabrous, or with a line of crisp or slightly sinuous hairs 0.1–0.5(2) mm long around the base.
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 to narrowly lanceolate or slightly oblanceolate, 3.5–6 mm, usually weakly keeled, glabrous throughout or keels and marginal veins softly puberulent to short-villous; area between veins smooth or scabrous, glabrous; short-villous, crisply puberulent, or loosely softly puberulent over the basal 67%; hairs usually 0.1–0.5 mm long; margins strongly inrolled below, broadly scarious above, glabrous; tips obtuse to broadly acute; blunt or pointed.
Anthers	0.6–1.1 mm, oblong.	1.5–3 mm.
2n	=28.

	Poa annua	Poa secunda
Distribution	[WildflowerSearch map] [BONAP county map]	[WildflowerSearch 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.	2 subspecies. Poa secunda is a common, highly variable, densely cespitose grass mainly of uplands. The spikelets are terete to slightly compressed, and the lemmas are more or less rounded over the back and usually hairy to scabrous throughout. Poa stenantha can be very similar, but its lemmas are a bit more strongly keeled and have hairs only on the veins. Callus hairs, if present, are 0.2–2 mm long. Hybrids between P. secunda and P. pratensis (P. × limosa) occur in moist, alkaline meadows in southeastern Oregon. They resemble P. secunda but are more or less rhizomatous and may have more strongly keeled lemmas. Hybrids with P. nervosa, called P. × multnomae, occur in the Columbia Gorge. They have more open panicles and generally grow in moister habitats than P. secunda. Puccinellia lemmonii and Poa secunda are superficially similar, but Puccinellia lemmonii has lower glumes that are less than 50% as long as the lowest lemma, and it grows in more strongly alkaline meadows and flats that are generally wet in spring. Poa secunda is a highly variable taxon. Its combination of asexual and sexual seed production produces multiple widespread, morphologically consistent forms that are sympatric. Many of these variants have been treated as species. However, intermediates can be found between all of them. Here we gather these forms into two categories treated as subspecies.
Source	Flora of Oregon, volume 1, page 453 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting	Flora of Oregon, volume 1, page 465 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. pringlei, P. reflexa, P. rhizomata, P. stenantha, P. suksdorfii, P. trivialis, P. unilateralis, P. wallowensis, P. wheeleri
Subordinate taxa		P. secunda ssp. juncifolia, P. secunda ssp. secunda
Synonyms		Poa canbyi
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	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 secunda

annual bluegrass

secund bluegrass

Habit

Plants annual, rarely biennial, 2–20(45)cm tall; cespitose.

Plants perennial, (10)15–120 cm tall; densely cespitose; basal leaf tufts (excluding culms) 2–20+ cm tall, glaucous or not.

Culms

nodes terete or weakly compressed.

slender to stout;

nodes terete, 0–2 exserted.

Basal branching

intravaginal.

intra- and extravaginal.

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 closed to 25% of their length, bases of basal sheaths glabrous;

collars smooth or scabrous, glabrous;

ligules 0.5–6(10)mm;

blades flat, folded, or involute, 0.4–3(5) mm wide, green to strongly glaucous; thin; soft and soon withering, or thick; firm and persisting; smooth, or scabrous mainly over the veins;

blades gradually reduced distally or the middle blades longest; uppermost blades 0.8–10(17)cm.

Inflorescences

1–7(10)cm;

branches ascending to spreading or reflexed.

erect or somewhat lax, narrowly lanceoloid to ovoid, usually contracted; more or less open in flower, infrequently remaining open at maturity, usually moderately congested, 2–25(30) cm;

spikelets 10–100+;

branches usually erect or ascending, infrequently spreading at maturity; (0.5)1–8(10) cm, 1–3 per node, with (1)2–20(60+) spikelets in distal 50–67%.

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.

usually narrowly lanceolate; more or less terete to slightly laterally compressed; (3.8)4–5 times as long as wide; (4)5–10 mm;

florets (2)3–5(10);

rachilla internodes usually 1–2 mm long; smooth to scabrous.

Glumes

lower glumes smooth, 1-veined.

broadly lanceolate;

keels indistinct;

lower glumes 3-veined.

Calluses

glabrous.

glabrous, or with a line of crisp or slightly sinuous hairs 0.1–0.5(2) mm long around the base.

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 to narrowly lanceolate or slightly oblanceolate, 3.5–6 mm, usually weakly keeled, glabrous throughout or keels and marginal veins softly puberulent to short-villous; area between veins smooth or scabrous, glabrous; short-villous, crisply puberulent, or loosely softly puberulent over the basal 67%;

hairs usually 0.1–0.5 mm long;

margins strongly inrolled below, broadly scarious above, glabrous;

tips obtuse to broadly acute; blunt or pointed.

Anthers

0.6–1.1 mm, oblong.

1.5–3 mm.

=28.

Poa annua

Poa secunda

Distribution

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch 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.

2 subspecies.

Poa secunda is a common, highly variable, densely cespitose grass mainly of uplands. The spikelets are terete to slightly compressed, and the lemmas are more or less rounded over the back and usually hairy to scabrous throughout. Poa stenantha can be very similar, but its lemmas are a bit more strongly keeled and have hairs only on the veins. Callus hairs, if present, are 0.2–2 mm long. Hybrids between P. secunda and P. pratensis (P. × limosa) occur in moist, alkaline meadows in southeastern Oregon. They resemble P. secunda but are more or less rhizomatous and may have more strongly keeled lemmas. Hybrids with P. nervosa, called P. × multnomae, occur in the Columbia Gorge. They have more open panicles and generally grow in moister habitats than P. secunda. Puccinellia lemmonii and Poa secunda are superficially similar, but Puccinellia lemmonii has lower glumes that are less than 50% as long as the lowest lemma, and it grows in more strongly alkaline meadows and flats that are generally wet in spring. Poa secunda is a highly variable taxon. Its combination of asexual and sexual seed production produces multiple widespread, morphologically consistent forms that are sympatric. Many of these variants have been treated as species. However, intermediates can be found between all of them. Here we gather these forms into two categories treated as subspecies.