Recognize Cenchrus as the familiar painful beach sandspurs...grasses with porcupine burrs that stick in dog fur and human flesh!

1. Spines with antrorse barbs, and setose...Pennisetum ciliare (C. ciliaris)

1. Spines with retrorse barbs...2

2. Spines of two distinct types: one type being a whorl of terete bristles at the base of the burr; the other bristles flat in one or more apparent whorls…Cenchrus echinatus

2. Spines all flattened and not with a distinct ring of terete bristles at the base of the spikelet (can have some round in C. tribuloides, but this with a raceme 2 cm in diam. vs. smaller)…3

3. Racemes > 2 cm diam...C. tribuloides (spikelet 1(2), 8-9 mm long)

3. Racemes 1 cm diam...4

4. Leaf blades usually 2(3.5) mm wide (well above the divergence from the sheath), glabrous; racemes usually not nestled in a subtending leaf sheath; ligule < 0.6 mm long; burrs uncrowded, with pubescence mostly confined to the spines, 3.5 mm diam…C. gracillimus

4. Some leaf blades > 3 mm wide, often pubescent adaxially, the racemes often (not always) nestled in a leaf sheath; ligule > 0.5 mm long; burrs crowded or uncrowded, usually pubescent on the outside at the base, 4-6 mm diam…C. spinifex (C. pauciflora, C. longispinus)