Flower:

Spike-like clusters 1 to 4 inches long at stem tips and arising from leaf axils in the upper stem. Flowers are enclosed in round, spine-covered burs, with 2 or 3 spikelets (flower clusters) per bur and 1 fertile flower per spikelet. Mostly hidden from view are the glumes (2 bracts at the base of a spikelet) and lemma (2 bracts surrounding a flower). Glumes are unequal in length and shorter than the lemma. Flower styles and stamens poke out from the tip of the bur. Burs are about ¼ inch in diameter (excluding the spines) and densely short-hairy; spines are barbed, 1/8 to nearly ¼ inch long, and often purplish.

Leaves and stems:

Leaves are all alternate, 2 to 7 inches long, about ¼ inch wide, rough on the upper surface, mostly smooth on the lower, flat or folded lengthwise, sometimes slightly rolled up on the edges.

The ligule (membrane where the leaf blade meets the sheath) is fringed with short, white hairs. The sheath is contracted where it meets the leaf, open at the front, sometimes with sparse, long hairs at the tip or along the edge near the top, keeled (ridged) at the back, somewhat flattened, and loosely surrounds the culm (stem). Nodes are hairless and green or red. Culms are hairless, multiple from the base, often branching, mostly covered by the sheaths, and light green but often tinged red towards the base. Culms may be erect to ascending, but typically sprawling and may root at the nodes.

Fruit:

The burs persist in fruit, the spines becoming very sharp when dried. They dry to a light tan and latch onto anything that passes by. Inside are 1 to 3 seeds.

Notes:

I hate this plant. If there is one within a mile of me it will find me, ruthlessly attack, and I'll be picking the burs out of my clothes and shoelaces for days. It is often found along sandy roadsides and railroad rights-of-way, where disturbance and unwitting victims like myself helps spread its seed. In some references C. longispinus goes by synonym Cenchrus carolinianus.