Plants annual or perennial but short-lived; tufted. Culms 30-100 cm, geniculate. Sheaths compressed, glabrous or sparsely pilose; ligules 0.5-1.4 mm; blades 3-28 cm long, (1)3-7.2 mm wide, glabrous or sparsely long-pilose adaxially. Panicles 3-5(8.5) cm; fascicles 5.5-10.2 mm long, 2.5-5 mm wide, imbricate, ovoid to globose, glabrous or sparsely to moderately pubescent; outer bristles, when present, mostly flattened; inner bristles 8-40 (rarely more), 2-5.8 mm long, 1-2 mm wide, fused at least 1/2 their length, forming a distinct cupule, the distal portions usually diverging from the cupule at multiple, irregular intervals, sometimes diverging at more or less the same level, ciliate at the base, pubescent, stramineous to mauve or purple, flattened. Spikelets 2-4 per fascicle, 3.5-5.9 mm, glabrous. Lower glumes 1-3.3 mm; upper glumes (2.8)3.5-5 mm, 5-7-veined; lower florets sometimes staminate; lower lemmas 3-5(5.9) mm, 5-7-veined; lower paleas sometimes reduced or absent; anthers 1.3-1.6 mm; upper lemmas 3.5-5(5.8) mm; anthers 0.5-1.2 mm. Caryopses about 2.5 mm long, 1-2 mm wide, ovoid. 2n = 34 (32).

Cenchrus spinifex is common in sandy woods, fields, and waste places throughout the southern United States and southwards into South America. It may be more widespread than shown in the northern portion of the contiguous United States because it has often been confused with C. tribuloides. Cenchrus spinifex differs from C. tribuloides in its glabrous or less densely pubescent fascicles, narrower inner bristles, and larger number of bristles. It has also been confused with C. longispinus, but differs in having shorter spikelets, fewer bristles overall, wider inner bristles, and outer bristles that are usually flattened rather than usually terete.

This sandbur prefers dry, sandy to very sandy soil and is found throughout the state where its habitat occurs. It is local where its habitat is absent and is frequent to common in the northern part of the state in the sandy areas, where it is a very obnoxious weed. It is found in cultivated grounds and waste places, in sandy railroad ballast, and along roadsides.

Common Name: coastal sandbur

Duration: Annual

Nativity: Native

Lifeform: Graminoid

General: Annual or short-lived perennial grass with weak, spreading stems 10-90 cm long, often freely branching and forming mats; deep, well-developed roots.

Vegetative: Blades flat or folded, 2-7 mm broad; ligule densely ciliate, membranous portion very short; collar margins villous.

Inflorescence: Compact, spikelike, 2-8 cm long, usually little-exserted from the sheath, mostly with 12-27 burs; burs variable, puberulent, 2.5-4 mm diameter, about as long as wide; spines highly variable, long and slender to short and broad, longest 4-6 mm, 2 spikelets per bur; first glume short, lanceolate-acuminate; second glume and sterile lemma lanceolate; lemma and palea lanceolate-acuminate, 4-5 mm long.

Ecology: Found on roadsides and waste places, mostly in sandy soil below 6,000 ft (1829 m); flowers June-October.

Distribution: Throughout the US, Mexico, Central America, and South America.

Notes: This primarily tropical genus is easily recognized by its dense, spikelike racemes of burs. Differs from C. longispinus by having shorter spikelets, fewer bristles (8-40 in C. spinifex vs. 45-75 in C. longispinus), wider inner bristles, and outer bristles that are flattened as opposed to terete. Distinguised from C. echinatus because the bristles on the bur do not form a ring.

Ethnobotany: Unknown

Etymology: Cenchrus is thought to be from Greek kenchros, millet, spinifex refers to its bearing spines.

Synonyms: Cenchurus carolinianus, Cenchurus incertus, Cenchurus parviceps, Cenchurus pauciflorus

Editor: SBuckley 2010, AHazelton 2015