Plants annual or perennial; cespitose, sometimes rhizomatous, occasionally stoloniferous. Culms 2–150 cm, erect or decumbent; nodes glabrous. Sheaths open; auriclesabsent or inconspicuous; ligules membranous, not ciliate; blades usually flat. Inflorescences dense, spikelike panicles, more than 1 spikelet associated with each node; branches often shorter than 2 mm, always shorter than 7 mm, stiff; pedicels shorter than 1 mm, sometimes fused; disarticulation above the glumes or, late in the season, beneath the glumes. Spikelets strongly laterally compressed, bases usually U-shaped, sometimes cuneate, with 1 floret; rachillas glabrous, sometimes prolonged beyond the base of the floret. Glumes equal, longer and firmer than the florets, stiff, bases not connate, strongly keeled, keels usually strongly ciliate, sometimes glabrous, sometimes scabrous, 3-veined, apices truncate to tapered, midveins often extending into short, stiff, awnlike apices; calluses blunt, glabrous; lemmas white, often translucent, not keeled, 5–7-veined, unawned, bases not connate, apices acute, entire, sometimes with a weak, subapical awn; paleas subequal to the lemmas, 2-veined; lodicules 2, free, glabrous, toothed; anthers 3; ovaries glabrous. Caryopses elongate-ovoid; embryos 1/6–1/4 the length of the caryopses. x = 7. Name from the Greek phleos, the name of a reedy grass.

Phleum is a genus of approximately 15 species, most of which are native to Eurasia. One species, P. alpinum, is native to the Flora region and six are introduced. One of the introduced species, P. pratense, has been established in the region for a long time. It is widely cultivated as a fodder grass, both in the Flora region and in other parts of the world. Phleum phleoides was first recognized as being present in the Flora region in 1990. Phleum exaratum has been reported from the United States. No specimens supporting the report have been seen. It resembles P. arenarium but has anthers 1.5–2 mm long, rather than 0.3–1.2 mm long, and an inflorescence that is rounded at the base.

Species of Phleum are sometimes mistaken for Alopecurus, but Alopecurus has obtuse to acute glumes that are unawned or taper into an awn, lemmas that are both awned and keeled, and paleas that are absent or greatly reduced. The species of Phleum that are most abundant in the Flora region are easily recognized by their strongly ciliate, abruptly truncate, awned glumes and adnate panicle branches. In addition, in Phleum the lemmas are not keeled and the paleas are always subequal to the lemmas.

SELECTED REFERENCES Humphries, C.J. 1978. Notes on the genus Phleum. Bot. J. Linn. Soc. 76:337–340; Kula, A., B. Dudziak, E. Sliwinska, A. Grabowska-Joachimiak, A. Stewart, H. Golczyk, and A.J. Joachimiak. 2006. Cytomorphological studies on American and European Phleum commutatum Gaud. (Poaceae). Acta Biol. Cracov., Ser. Bot. 48:99–108.