7. Panicum commutatum Schult.
Pl. 165 e,
f; Map 668
Dichanthelium commutatum (Schult.) Gould
Plants perennial, without rhizomes,
forming tufts.
Flowering stems 20–80 cm long, erect or ascending, unbranched or the upper
nodes becoming sparsely branched during the summer and autumn, the nodes and
internodes glabrous or with sparse, short hairs. Foliage in a
dense rosette of shorter, slightly broader leaves at the base and longer,
somewhat narrower leaves well distributed along the main stems, those of the
later branches usually slightly shorter and narrower than those of the main
stem leaves. Leaf sheaths glabrous or hairy, sometimes only at the tip
and along the margins, the ligule absent or 0.3–1.0 mm long and consisting of a
line or band of hairs. Leaf blades of the main stems 4–15 cm long, 5–25 mm
wide, mostly spreading, broadest near the base, heart‑shaped and somewhat
clasping at the base, firm, hairy along the margins near the base, at least
some of the hairs with pustular bases, glabrous on the surfaces, the midvein
and larger lateral veins not raised. Inflorescences 5–15 cm long, the earlier
ones larger than the later ones, the branches loosely ascending to spreading,
mostly rebranched 1 or more times, not spikelike or 1‑sided, the
spikelets appearing mostly long‑stalked at the tips of the branches. Spikelets 2.1–3.2 mm long, elliptic in outline. Lower glume
0.7–1.6 mm long, 1/3–1/2 as long as the spikelet, broadly ovate, bluntly
pointed at the tip, glabrous, nerveless or faintly 1–5‑nerved. Upper
glume 2.0–3.2 mm long, elliptic, rounded to bluntly pointed at the tip, 5–9‑nerved,
hairy or less commonly glabrous. Lowermost floret sterile and with a reduced,
inconspicuous palea, the lemma 2.0–3.2 mm long, elliptic, rounded or bluntly
pointed at the tip, 5–9‑nerved, hairy or less commonly glabrous. Fertile
floret 1.8–2.4 mm long, elliptic, rounded to bluntly pointed at the tip. Anthers 0.3–1.4 mm long. 2n=18. May–August
(vernal), June–November (autumnal).
Scattered in the Ozark and Mississippi Lowlands Divisions,
uncommon farther north (eastern U.S.
west to Michigan and Texas;
Mexico).
Bottomland forests, mesic to dry upland forests, and banks of
streams, on acidic substrates.
Two weakly differentiated varieties are present in Missouri.