Plants annual, with soft bases, without rhizomes. Flowering
stems (20–)40–200 cm long, often slightly flattened, glabrous. Leaf sheaths
usually somewhat keeled, hairy along the margins and usually roughened on the
surface, the ligule 1–3 mm long. Leaf blades 10–50 cm long, 6–22 mm wide, flat,
the upper surface roughened and also sparsely to more commonly densely
pubescent with long, pustular‑based hairs, the undersurface roughened.
Inflorescences 3–20 cm long, frequently nodding or drooping from near the base,
the very short branches reduced to clusters of spikelets and the inflorescence
thus appearing as a cylindrical spike, the main axis pubescent with short,
upwardly pointing hairs, the spikelets subtended by 1–3(–6) green bristles,
these 4–12 mm long. Spikelets 2.4–3.0 mm long, disarticulating below the
glumes. Lower glume 0.8–1.5 mm long. Upper glume 1.8–2.4 mm long. Lowermost
floret usually sterile, 2.2–2.7 mm long. Fertile floret with the lemma 2.3–2.7
mm long, with noticeable, fine cross‑wrinkles on the surface. Anthers 0.5–1.1
mm long. 2n=36. July–October.
Introduced, scattered to common nearly throughout Missouri (native of Asia; introduced and weedy in the northeastern U.S. west to South Dakota and Arkansas). Banks of rivers; also crop fields, fallow fields, old
fields, gardens, roadsides, and railroads.
This species probably was introduced into the United States during the early 1920s as a contaminant in grain seed (Rominger, 1962). It
spread quickly along railways and roads and was collected in Missouri as early
as 1932, in St. Charles County. It is a serious weed of crop fields,
particularly shorter crops, such as soybeans.
Steyermark (1963) noted a putative hybrid between this
species and S. viridis from Lewis County, but the plant appears to be a
somewhat less pubescent variant of S. faberi. The presence of such
hybrids in Missouri requires confirmation.