Plants perennial or annual; cespitose or tufted. Culms 4-65 cm, erect, slender. Leaves linear, flat, usually becoming folded and filiform; ligules membranous, ciliate. Inflorescences terminal, unilateral linear spikes or spikelike racemes, with 1 spikelet per node, exceeding the leaves; rachises visible, not concealed by the spikelets. Spikelets appressed, in 2 rows along 1 side of the rachises, with 3-20 bisexual florets, distal florets sterile or staminate; disarticulation above the glumes and between the florets. Glumes unequal, 1(3)-veined; lemmas 1-3-veined, backs slightly keeled or rounded, apices lobed or bifid, mucronate or awned from between the lobes, lateral veins sometimes also excurrent, awns usually straight; anthers 1-3. x = 10. Name from the Greek treis, three, and pogon, beard, alluding to the hairs at the bases of the three lemma veins found in many of its species.

Tripogon is a genus of approximately 30 species, most of which are native to the tropics of the Eastern Hemisphere, especially Africa and India, but with one, Tripogon spicatus, native to the Western Hemisphere.

1.   Tripogon spicatus (Nees) Ekman
American Tripogon

Plants perennial; cespitose. Culms (4.5)6-34 cm; nodes 2-3, glabrous. Leaves mostly basal; sheaths mostly glabrous, but with tufts of hairs flanking the collar; ligules 0.2-0.3 mm, truncate; blades 1.9-10 cm long, 0.2-1.1 mm wide, glabrous or the adaxial surfaces and margins sparsely pubescent. Inflorescences (1.5)4-10 cm long, 1.5-3.5 mm wide, with (6)13-22 spikelets; pedicels 0-0.5 mm, glabrous. Spikelets 4.5-12 mm long, 1-1.3 mm wide, with 5-14 florets; rachilla internodes glabrous except for an apical tuft of hairs. Glumes unequal, exceeded by the basal florets; lower glumes (1.2)1.5-2.4 mm, glabrous, 1-veined, scabridulous over the veins; upper glumes 1.9-2.6 mm, glabrous, 1-veined; lowest lemmas 2.3-3.1 mm, 3-veined, apical sinuses 0.1-0.3 mm deep; awns 0.2-0.9 mm, straight; paleas 1.6-2.4 mm, glabrous on the back and minutely pubescent on the margins; anthers 3, 0.3-0.4 mm, yellow to purple. Caryopses 1-1.5 mm, reddish-brown. 2n = 20.

Tripogon spicatus grows in shallow rocky soils, usually on granite outcroppings, occasionally on limestone. The flowering period, April-July (October, November), apparently depends on rainfall. Its range includes the West Indies, Mexico, and South America, in addition to central Texas.