Plants cespitose, with knotty, shortly rhizomatous bases. Culms
60-125 cm. Sheaths rounded or the basal sheaths keeled, glabrous, except
for a few hairs on either side of the collar; ligules 1-2 mm, membranous,
ciliate; blades 2-5 mm wide, elongate, usually involute distally. Panicles
8-16(20) cm long, 1.5-4 cm wide, not dense; branches to 8(10) cm, erect
to divergent, stiff; pedicels shorter than 1 mm. Spikelets 4-6 mm
long, pale to dark purple, with 4-6 florets. Glumes 1-veined; lower
glumes 4-4.5 mm; upper glumes about 5 mm; lemmas 3-4 mm, veins
pubescent to midlength or beyond, midveins excurrent, lateral veins often excurrent;
paleas 3-3.5 mm, veins ciliolate, bases bowed-out; anthers 1-1.5
mm. Caryopses 1.5-1.8 mm. 2n = 40.
Tridens ambiguus grows on the southeastern coastal plain, from North Carolina
to Texas. It is usually found in mesic to perennially moist soils of pine flatwoods
and pine-oak savannahs, in seasonally inundated depressions, and at the margins
of pitcher plant bogs, often in disturbed sites.