Plants perennial, monoecious, with short, stout rhizomes,
forming clumps. Flowering stems 70–250 cm long, erect or ascending, mostly
unbranched, circular in cross‑section or slightly flattened, glabrous.
Leaf sheaths rounded to keeled on the back, glabrous, the ligule a short
membrane with a hairy (fringed) margin. Leaf blades 10–70 cm long, 7–20 mm
wide, glabrous or somewhat hairy at the base, flat, the midvein noticeably
thickened. Inflorescences consisting of 1–4 dense, spikelike racemes, these in
a palmate (or nearly so) cluster at the tip of the stem, 10–30 cm long, with
staminate spikelets toward the tip and pistillate spikelets in the basal
1/3–1/2, disarticulating at the axis joints, the staminate portion often shed
as an intact unit. Staminate spikelets paired along 1 side of the flattened
axis, both sessile or very short‑stalked, similar in size and appearance,
the glumes 5–10 mm long, longer than the florets, elliptic, usually narrowed to
2 minute teeth at the tip, faintly 9–16‑nerved and usually 2‑keeled
near the margins, firm, glabrous or minutely hairy at the tip. Staminate lemmas
4–9 mm long, elliptic‑ovate, thin, awnless. Anthers 3–7 mm long.
Pistillate spikelets single, closely appressed to (appearing sunken into)
concave portions on 1 side of the axis, with 2 florets, the lowermost usually sterile
and reduced, the uppermost fertile. Glumes 5–9 mm long, the outer (lowermost)
glume wrapped around and enclosing the rest of the spikelet, broadly ovate in
outline, pointed or narrowed to 2 minute teeth at the tip, thick, hardened and
bony at maturity, faintly many‑nerved, glabrous (the axis joints with
small tufts of hair at the spikelet bases), shiny. Pistillate lemmas and
paleas, 3–7 mm long, narrowly ovate, membranous, awnless. Fruits enclosed in
the persistent glumes and axis joints. 2n=18, 36, 45, 54, 72, 90, 108; 2n=36
in Missouri. May–September.
Scattered throughout the state, most abundantly in the
Unglaciated Plains Division (eastern U.S. west to Nebraska and Texas; south to South America). Upland prairies, glades, savannas, and less commonly
openings and margins of mesic to dry upland forests; also roadsides, railroads,
fallow fields, margins of crop fields, and disturbed, open areas.
Tripsacum dactyloides is a widespread, morphologically and cytologically variable
species that has been split into a number of poorly defined varieties by some
workers (de Wet et al., 1982). If such varieties are accepted, then the Missouri plants are all var. dactyloides. Missouri populations examined thus far are
of the sexual, diploid type, (Anderson, 1944; Farquharson, 1955), but the
widespread eastern and southern tetraploid race can produce seed apomictically
and may eventually be found in the state. Gama grass is an important component
of upland prairie vegetation and is considered highly desirable both as fodder
for livestock and production of hay.