Plants with short, scaly rhizomes. Culms 50-90 cm tall, usually less than 1 mm thick, not rooting or branching at the lower nodes, usually glabrous. Ligules about 0.5 mm; blades 9.5-25 cm long, 1-3 mm wide, usually folded, without a longitudinal stripe of white, spongy tissue. Peduncles 3-7 cm; rames 2-5.5 cm, with 5-14 spikelets, partially to fully exserted, collars neither elongate nor particularly narrow. Sessile spikelets 4-7.5 mm; calluses sparsely pubescent, hairs to 1.5 mm; awns 2.5-10 mm; upper lemmas membranous throughout, apices cleft for about 1/4 of their length. Pedicels 3.5-5 mm, ciliate, hairs to 2.3 mm, pedicel bases 0.1-0.2 mm wide, flaring above midlength to about 0.5 mm wide, tending to curve outward, rames appearing somewhat open. Pedicellate spikelets 2.5-5.5 mm, unawned or with awns to 1 mm.

Schizachyrium rhizomatum grows in open glades and on the margins of pine woodlands, and is endemic to Florida. It is restricted to thin, oölitic soils that are often saturated with water and is a common species in marl prairies of Monroe and Dade Counties, Florida. On the Florida Keys, it forms sparse stands, occasionally mixed with Andropogon gracilis. Modifed May 30, 2009 on basis of literature review by Ann Johnson for the Florida Natural Are Inventory.