5. Panicum capillare
L. (common witchgrass)
Pl. 170 a–c;
Map 666
P. capillare var. occidentale Rydb.
Plants annual, forming tufts. Flowering stems 15–70 cm long,
relatively slender, more or less circular in cross‑section, sparsely
hairy near the nodes. Leaves scattered along the stems. Leaf sheaths rounded on
the back, hairy, the hairs usually without pustular bases, the ligule 0.5–2.0
mm long, a line or band of hairs (sometimes with a minute membrane at the
base). Leaf blades 4–25 cm long, 6–17 mm wide, relatively soft, ascending to
spreading, hairy, at least toward the base, flat. Inflorescences 10–35 cm long,
usually more than 1/2 as long as the entire flowering stem, less than 2 times
as long as wide, often breaking off at the base and becoming a “tumbleweed” at
maturity, the primary branches ascending to mostly spreading, not spikelike,
with tufts of hairs at the bases, rebranched several times, the spikelets not
appearing 1‑sided, mostly single at the branch tips, mostly long‑stalked,
not curved or angled with respect to their stalks. Spikelets 1.8–3.0 mm long,
elliptic in outline, tapered to a relatively long, narrow, sharp point at the tip,
glabrous. Lower glume 0.8–1.5 mm long, 1/3–1/2 as long as the rest of the
spikelet, ovate, sharply pointed at the tip, 3–7‑nerved. Upper glume
1.8–3.0 mm long, elliptic, tapered to a relatively long, narrow, sharp point at
the tip, 7‑ or 9‑nerved. Lowermost floret sterile
and without a palea, the lemma 1.8–3.0 mm long, elliptic, 7‑ or 9‑nerved.
Fertile floret 1.8–2.3 mm long, elliptic, bluntly pointed at the tip, light
yellow or straw‑colored at maturity. Anthers 0.7–1.0 mm
long. Fruits 1.4–2.0 mm long, narrowly elliptic to
elliptic in outline. 2n=18. July–October.
Scattered to common throughout the state (throughout most of
the U.S. and adjacent Canada; introduced in South America and Europe). Glades (on both calcareous and acidic
substrates), upland prairies, openings of mesic to dry upland forests, and
gravel bars and banks of streams; also fallow fields, roadsides, railroads, and
open, disturbed areas