Plants cespitose, with knotty, rhizomatous bases. Culms 50-90 cm tall, 1-2.9 thick, erect, glabrous; nodes usually 3. Sheaths mostly glabrous, mar¬gins ciliate distally; collars glabrous, often with tufts of hair to 1.5 mm on the margins; ligules 0.5-1.5 mm, membranous, ciliate, cilia 1-2 mm, slightly longer at the leaf margins; blades 10-50 cm long, usually tightly convolute and 0.4-1 mm in diameter, 2-4 mm wide when flat, erect, abaxial surfaces smooth, adaxial surfaces usually glabrous. Panicles 10-20 cm long, 1-5 cm wide, bases sometimes included in the leaf-sheaths; branches ascending to spreading, longest lower branches 4-12 cm. Glumes subequal, 6.3-13 mm, linear-lanceolate, 3-veined, midveins smooth, scabrous, or with stiff hairs, varying within a panicle, apices acuminate; florets 5.5-8 mm long, about 0.8-1.3 mm thick, fusiform; calluses 0.3-0.6 mm, blunt, strigose, hairs 0.5-0.8 mm; lemmas pubescent on the proximal 1/2, the pubescence over the midvein extending to the awn, hairs 0.5-0.8 mm, distal portion glabrous, tapering to the apices, apices with 0.7-1 mm hairs around the base of the awn; awns 11-23 mm, glabrous or scabrous, usually twice-geniculate; paleas 3.5-6.5 mm, 3/4 - 9/10 as long as the lemmas, pubescent over the central portion, apices involute; lodicules 3; anthers 3-4 mm, penicillate. Caryopses about 3 mm long, 1-1.4 mm thick; style bases upright, centric. 2n = unknown.
Amelichloa clandestina is native from northern Mexico to Colombia. It has been accidentally introduced to pastures and roadsides in Texas, and is now established there. Reports from California need to be checked. They may reflect misidentifications of A. brachychaeta, which differs from A. clandestina in its shorter ligules, florets, and anthers.
"decumbent" is not a number.