Sandburs are easily recognized by their distinctive burs, which are formed by fusion of sterile branches from the flowering head. Each bur encloses 2-3 (-4) spikelets. Burs catch in the fur of passing animals to disperse the seeds from the parent plant and also hitchhike on socks and pant legs—you won’t soon forget an encounter with a sandbur! Sandburs are typically found in sandy sites, abandoned fields, and recently disturbed areas. Longspine sandbur invades recently disturbed areas and will persist for 2-3 years before being replaced by other species. Sandburs have a wide tolerance for soil type, soil moisture content, and plant neighbors, which is why this species is such a successful weed. In Iowa, longspine sandbur is widespread and common and is also widespread in the eastern and central parts of the United States. Its range extends north into Canada, south through Mexico to northern South America and into the West Indies. It has also formed naturalized populations in western Europe, Africa, and Australia. Longspine sandbur flowers from July to September in Iowa, rarely earlier.

Etymology: Cenchrus from the Greek kenchros = a kind of millet; longispinus from the Latin longus = long and spina = spine, referring to the well-developed spines projecting from the distinctive bur.

Plants annual. Culms 10-80 cm tall, tufted but sometimes decumbent, the branches sometimes forming a mat and rooting at the nodes; internodes often flattened. Leaves with sheaths open, strongly compressed and keeled, with long hairs on the upper margins and at the margin where the blade and sheath meet; ligules a line of hairs 0.6-1.5 mm long; blades 5-21.5 cm long, 3-6 mm wide, flat, upper surface smooth or roughened. Panicles terminal, well exserted or partially enclosed in the sheath below, compact, oblong, 4-8 cm long, 1-2 cm wide; burs more or less globose, hairy, 5-8 mm long, 3.5-6 mm wide; spines (bristles) slender, numerous per bur, often purple-tinged, 3-6.5 mm long, 0.5-1.4 mm wide at base, forming a distinct cupule, apical portions diverging at irregular intervals from the cupule, outer spines at base of the bur shorter and thinner than those on the body of the bur, 1.5-2.5 mm long, overlapping, terete, downwardly curved. Spikelets 2-3 (-4) per bur, dorsally compressed, the tips often visible protruding from the top of the bur; florets 2, the upper fertile and the lower sterile or often staminate. Chromosome number 2n = 34, 36.