Poa annua

L.
Common names: Annual bluegrass
Introduced
Synonyms: Poa annua var. reptans Poa annua var. aquatica
Treatment appears in FNA Volume 24. Treatment on page 519.
Please click on the illustration for a higher resolution version.
Illustrator: Sandy Long

Copyright: Utah State University

Plants usually annual, rarely surviving for a second season; not rhizomatous, sometimes stoloniferous, densely tufted. Basal branching intravaginal, innovations common, similar to the culms. Culms 2-20 (45) cm, prostrate to erect, slender; nodes terete, usually 1 exserted. Sheaths closed for about 1/3 their length, terete or weakly compressed, smooth; ligules 0.5-3 (5) mm, smooth, glabrous, decurrent, obtuse to truncate; blades 1-10 cm long, 1-3 (6) mm wide, flat or weakly folded, thin, soft, smooth, margins usually slightly scabrous, apices broadly prow-shaped. Panicles 1-7 (10) cm, lengths 1.2-1.6 times widths, erect; nodes with 1-2 (3) branches; branches ascending to spreading or reflexed, straight, terete, smooth, with crowded or loosely arranged spikelets. Spikelets 3-5 mm, laterally compressed; florets 2-6; rachilla internodes smooth, glabrous, concealed or exposed, distal internodes less than 1/2 (3/4) the length of the distal lemma. Glumes smooth, distinctly keeled, keels smooth; lower glumes 1-veined; upper glumes shorter than or subequal to the lowest lemma; calluses glabrous; lemmas 2.5-4 mm, lanceolate, distinctly keeled, smooth throughout, the keels, marginal veins, and, usually, lateral-veins crisply puberulent to long-villous, rarely glabrous throughout, lateral-veins prominent, intercostal regions glabrous, margins smooth, glabrous, apices obtuse to acute; palea keels smooth, usually short to long-villous, rarely glabrous; anthers 0.6-1.1 mm, oblong prior to dehiscence, those of the upper 1-2 florets usually vestigial. 2n = 28.

Distribution

Conn., N.J., N.Y., Wash., Va., Mich., Del., D.C., Wis., Alta., B.C., Greenland, Man., N.B., Nfld. and Labr., N.S., N.W.T., Ont., P.E.I., Que., Sask., Yukon, W.Va., Pacific Islands (Hawaii), Mass., Maine, N.H., R.I., Vt., Fla., Wyo., N.Mex., Tex., La., Tenn., N.C., S.C., Pa., Calif., Nev., Puerto Rico, Colo., Md., Alaska, Ala., Kans., N.Dak., Nebr., Okla., S.Dak., Ark., Ill., Ga., Ind., Iowa, Ariz., Idaho, Mont., Oreg., Ohio, Utah, Mo., Minn., Miss., Ky.

Discussion

Poa annua is one of the world's most widespread weeds. It thrives in anthropomorphic habitats outside of the arctic. A native of Eurasia, it is now well established throughout most of the Flora region.

Poa annua is a gynomonoecious tetraploid (possibly rarely polyhaploid), and is thought to have arisen from hybridization between P. infirma (see next) and P. supina (p. 521) (Tutin 1952). It is similar to P. infirma, differing in having larger anthers. It differs from P. chapmaniana (p. 534) in having glabrous calluses and three larger anthers, rather than one. Forms with glabrous lemmas occur sporadically within populations.

Selected References

None.

Lower Taxa

None.

"decumbent" is not a number.

... more about "Poa annua"
membranous +  and scarious +
puberulent +, hispidulous +, hairy +  and glabrous +
5 cm50 mm <br />0.05 m <br /> (?) +
0.06 cm0.6 mm <br />6.0e-4 m <br /> (0.11 cm1.1 mm <br />0.0011 m <br />) +
Obtuse (?) +  and Acute (?) +
Robert J. Soreng +
1 (?) +  and 3 (?) +
straight +
basal +  and terminal +
keeled +  and rounded +
strigose +  and glabrous +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
1 cm10 mm <br />0.01 m <br /> (10 cm100 mm <br />0.1 m <br />) +
not evident +
folded +  and flat +
thin;1mm;3mm +
ascending;spreading or reflexed +
hispidulous +, glabrous +, smooth or +  and sparsely densely scabrous +
Annual bluegrass +
unbranched +  and hollow +
prostrate +  and erect +
compressed +  and terete +
slender +
2 cm20 mm <br />0.02 m <br /> (20 cm200 mm <br />0.2 m <br />) +
not woody +
Conn. +, N.J. +, N.Y. +, Wash. +, Va. +, Mich. +, Del. +, D.C. +, Wis. +, Alta. +, B.C. +, Greenland +, Man. +, N.B. +, Nfld. and Labr. +, N.S. +, N.W.T. +, Ont. +, P.E.I. +, Que. +, Sask. +, Yukon +, W.Va. +, Pacific Islands (Hawaii) +, Mass. +, Maine +, N.H. +, R.I. +, Vt. +, Fla. +, Wyo. +, N.Mex. +, Tex. +, La. +, Tenn. +, N.C. +, S.C. +, Pa. +, Calif. +, Nev. +, Puerto Rico +, Colo. +, Md. +, Alaska +, Ala. +, Kans. +, N.Dak. +, Nebr. +, Okla. +, S.Dak. +, Ark. +, Ill. +, Ga. +, Ind. +, Iowa +, Ariz. +, Idaho +, Mont. +, Oreg. +, Ohio +, Utah +, Mo. +, Minn. +, Miss. +  and Ky. +
1/4 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
sometimes longer +
1 +  and 2 +
compressed +
reduced +
1-3(5)-veined +
shorter or longer +
subtending +
unequal +
distributed +
uncinate +
0.1 cm1 mm <br />0.001 m <br /> (?) +
0 +  and 1/6 +
Oval (?) +  and Round (?) +
milky white +  and slightly greenish +
glabrous +, crisply puberulent +  and long-villous +
5(7-11)-veined +
keeled +  and lanceolate +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
membranous +
erose +  and entire +
white +  and milky white or hyaline +
obtuse +  and truncate +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
membranous +
inconspicuous +
lobed +  and lanceolate +
milky white +  and slightly greenish +
concealed +  and prominent +
2 +  and 1 +
well-developed +
2-keeled +
subequal +
10 cm100 mm <br />0.1 m <br /> (?) +
ovoid +  and pyramidal +
1 cm10 mm <br />0.01 m <br /> (7 cm70 mm <br />0.07 m <br />) +
dry +  and fleshy +
exposed +  and concealed +
compressed +  and terete +
Introduced +
not bulbiferous +
arranged +  and crowded +
many +, 1 +  and 100 +
compressed +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
1 (?) +  and 3 (?) +
simple +  and compound +
2 (?) +  and 3 (?) +
Poa annua var. reptans +  and Poa annua var. aquatica +
Poa annua +
Poa sect. Micrantherae +
species +
membranous +
parallel +  and converging +
stoloniferous +  and not rhizomatous +
aquatic +  and terrestrial +