Culms 70-130 cm, mostly glabrous, sometimes pubescent below the nodes; nodes yellow-ish, glabrous. Sheaths glabrous; ligules blunt to acute, of basal leaves 0.4-0.7 mm, of upper leaves to 3 mm; blades 15-30 cm long, 0.8-1.5 mm wide, usually involute and 0.5 mm in diameter, 3-veined, abaxial surfaces usually glabrous and smooth, sometimes scabrous, adaxial surfaces usually scabrous over the veins, sometimes smooth, sometimes hairy. Panicles 10-31 cm, open, with 10-50 spikelets; pedicels 15-20 mm, scabrous. Glumes 15-22 mm, (3)5-veined; florets 13.5-22 mm long, 1-2 mm thick, terete; calluses 3.5-8 mm, sharp, strigose, hairs golden brown at maturity; lemmas glabrous, tan to brown at maturity, mostly smooth, sharply tuberculate distally, contracted below the crown; crowns 0.6-0.7 mm wide, hairy, hairs 0.2-0.6 mm; awns 62-120 mm, persistent, twice-geniculate; paleas 9-12 mm; lodicules 2; anthers 4-7 mm. 2n = unknown.
Piptochaetium avenacioides grows in dry woods, generally on sandy ridges. It is endemic to Florida, growing primarily in the central peninsula. Morphologically, it is very similar to P. avenaceum, differing only in its larger size and more restricted distribution.