Apera

Plants annual; tufted or the culms solitary. Culms 5-120 cm, erect or geniculate, glabrous. Leaves mostly cauline; sheaths open, rounded to slightly keeled; collars glabrous, midveins continuous; auricles absent; ligules membranous, often lacerate to erose; blades flat or weakly involute, glabrous. Inflorescences terminal panicles; branches strongly ascending to divergent. Spikelets pedicellate, slightly laterally compressed, with 1 floret, rarely more, distal florets, if present, vestigial; rachillas prolonged beyond the base of the floret as a bristle, rarely terminating in a vestigial floret; disarticulation above the glumes, beneath the floret. Glumes unequal, lanceolate, scabrous on the distal 1/2, unawned; lower glumes 1-veined; upper glumes slightly shorter than to slightly longer than the florets, 3-veined; calluses blunt, glabrous or sparsely hairy; lemmas firmer than the glumes, folded to nearly terete, obscurely 5-veined, marginal veins not excurrent, apices entire, awned, awns subterminal; paleas about 3/4 as long as to equaling the lemmas, hyaline, 2-veined; lodicules 2, free, glabrous, usually toothed; anthers 3; ovaries glabrous. Caryopses shorter than the lemmas, concealed at maturity, 1.2-2 mm, ellipsoidal, slightly sulcate; hila broadly ovate, 1/5 the length of the caryopses. x = 7.

Distribution

Conn., N.J., N.Y., Wash., Del., D.C, Wis., Wyo., N.Mex., Pacific Islands (Hawaii), Ohio, Pa., B.C., Ont., Mass., Maine, Nev., Colo., Md., Calif., Oreg., Vt., Ill., Ind., Ariz., Idaho, Mont., Tex., Utah, Mo., Mich., Ky.

Discussion

Apera is genus of three species, native to Europe and western Asia. It is similar to Agrostis. It differs in its firm lemmas; paleas that are always present and equal to the lemma, or nearly so; and prolonged rachillas. In North America, two species have been introduced, growing as weeds in lawns and disturbed ground, and in grain fields.

Selected References

Warwick, S.I., B.K. Thompson, and L.D. Black. 1987. Genetic variation in Canadian and European populations of the colonizing weed species Apera spica-venti. New Phytol. 106:301-317.

Lower Taxa

Apera interrupta, Apera spica-venti

Key

1	Anthers 0.3-0.5 mm long; panicles contracted, 0.4-3 cm wide; most branches spikelet-bearing to within 2 mm of the base	Apera interrupta
1	Anthers 1-2 mm long; panicles pyramidal, 2-15 cm wide; branches naked at the base for 5 mm or more	Apera spica-venti