2. Cenchrus longispinus (Hack.) Fernald (sandbur)

Pl. 160 c, d; Map 648

Plants annual. Flowering stems 10–80 cm long. Leaf blades 4–15(–20) cm long, 3–7 mm wide. Inflorescences 4–10 cm long, with 4–18 spikelet clusters, these forming more or less globose burs at maturity, subtended by stout bristles and flattened spines, with (1)2–3 spikelets. Bristles and spines 3–7 mm long, united to above the middle, in two series, a longer, ascending to spreading, inner series and a shorter, downward‑pointing, outer series. Spikelets 5.5–7.8 mm long. Lower glume 1–4 mm long. Upper glume 4–6 mm long, 3‑ or 5‑nerved. Sterile or staminate floret with the lemma 4.0–6.5 mm long. Fertile (perfect) floret with the lemma 5.3–7.6 mm long. Anthers 0.7–2.1 mm long, those of the upper (perfect) floret noticeably shorter than those of the lower floret (when staminate). Fruits 2.2–3.5 mm long. 2n=34, 36. May–October.

Scattered nearly throughout Missouri (native of the U.S., Canada, Mexico, Central America, and the Caribbean Islands; introduced in Europe, Africa, and Australia). Sand prairies; also roadsides, railroads, fallow fields, margins of crop fields, and open, disturbed areas, especially on sandy substrates.

The spiny burs of this species are easily detached from the inflorescence and can cause sudden, painful injury to feet, hands, and other parts of the human body. They are readily transported on clothes or other objects, including animal fur, and can cause serious injury to the noses, eyes, and mouths of cattle and other animals that come into accidental contact with them while grazing or sniffing the ground. Steyermark (1963) noted that burs lodging in the wool of sheep can damage the fleece.