4. Panicum boscii
Poir.
Pl. 167 c,
d; Map 665
P. boscii var. molle (Vasey) Hitchc. & Chase
Dichanthelium boscii (Poir.) Gould & C.A. Clark
D. boscii var. molle (Vasey) Mohlenbr.
Plants perennial, with rhizomes
short or absent, forming tufts or more commonly clumps. Flowering stems 30–70 cm long,
erect or ascending to arched, unbranched or the upper nodes becoming sparsely
branched during the summer and autumn, the nodes with a conspicuous beard of
downward‑pointing hairs, the internodes glabrous or minutely hairy. 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 somewhat shorter and narrower than those of
the main stem leaves. Leaf sheaths usually hairy along
the margins, glabrous or hairy on the surface, the ligule 0.5–1.0 mm long, a
line or band of hairs. Leaf blades of the main stems 6–14 cm long, (9–)14–33
mm wide, ascending to spreading, heart‑shaped and somewhat clasping at
the base, firm, hairy along the margins near the base, glabrous or hairy on the
surfaces, the midvein and larger lateral veins prominent and raised.
Inflorescences 4–25 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 3.7–5.2 mm long,
elliptic‑obovate in outline. Lower glume 1.4–2.5 mm long, 1/3–1/2
as long as the spikelet, ovate, sharply pointed at the tip, glabrous or
sparsely hairy, nerveless or faintly 1–5‑nerved. Upper glume 3.5–5.0 mm
long, elliptic, rounded at the tip, 5–9‑nerved, hairy. Lowermost floret
sterile or staminate and with a well‑developed, conspicuous palea, the
lemma 3.5–5.2 mm long, elliptic, rounded at the tip, 5–9‑nerved, hairy.
Fertile floret 3.2–4.0 mm long, elliptic, rounded to bluntly pointed at the
tip. Anthers 0.3–1.4 mm long. 2n=18, 36. May–July (vernal), July–October (autumnal).
Scattered, mostly south of the
Missouri River (eastern U.S.
west to Illinois, Missouri,
and Texas). Mesic to dry
upland forests and less commonly ledges of shaded bluffs.
Panicum boscii is a characteristic species of ravines in the Ozarks. It is
distinguished from P. clandestinum and P. latifolium, the two
other Missouri
species having relatively large, broad leaf blades with clasping bases, by its
bearded stem nodes and longer spikelets. Some specimens of P. latifolium
also have noticeably hairy nodes, but in these the hairs are not markedly
differentiated from those of the internodes. Other species with clasping leaf
bases, such as P. boreale and P. commutatum, have generally
somewhat narrower leaf blades and shorter spikelets.