Dune Sandspur is a stout, annual grass species. The stems are trailing or decumbent, and up to 1 meter long, with short (up to 14 cm), wide (to 14 mm) leaves and soft-hairy leaf sheaths. There is a single spikelet (occasionally 2) enclosed in a densely hairy bur with from 15 to 40 barbed spines (treacherous to the barefoot), each from 4 to 8 mm long (Gleason and Cronquist 1991).

Dune sandspur may be identified vegetatively, though fruits are best for quick identification. Barefoot dune explorations may result in an unintended, painful discovery of this species.

Cenchrus is our only genus of grass with spiny burs. C. longispinus, our other native sandspur in New York, is much more widespread than C. tribuloides. It has less hairy spikelets with more (45 to 75) spines per bur, and has 2 to 3 spikelets per bur.