Grass family (Poaceae)
Description: This native grass is a summer annual with branching culms up to 2½' long; it produces several culms from the base that sprawl across the ground. The culms are light green, hairless, terete, and mostly covered by the sheaths of the leaves; their nodes are green or reddish green and glabrous. The blades of the alternate leaves are up to 6" long and 1/3" across; they are dull green, hairless, flat, broadest near the base, and linear in shape. The upper surface and margins of each leaf blade are scabrous. The sheaths of the leaves are dull green, mostly hairless, keeled, and somewhat flattened; a few white hairs may occur at the apex of some sheaths. Each culm and its upper branches terminate in individual racemes of flowers; each flower is enclosed in a spiny bur. Each raceme has a zigzag stalk up to 4" long with 4-20 burs on short pedicels. Each bur is about ¼" across (excluding the spines), yellowish green, and either globoid or globoid-ovoid in shape; it consists of 2 spiny rounded bracts that enclose 2-3 flowers. The outer surface of each bur has spines up to ¼" long and it is more or less pubescent. Each flower has 2 glumes and 2 lemmas; they are translucent with several fine green veins. The lemmas are lanceolate with a convex outer surface; they are about the same length as the bur. The glumes are smaller in size. The anthers and plumose styles of the flowers are exerted from the apex of the burs. The blooming period occurs from mid-summer to early fall. The flowers are wind-pollinated. After cross-pollination, the burs turn brown as their grains ripen. The root system is fibrous.
Cultivation: The preference is full or partial sun, mesic to dry conditions, and open sandy soil. Sandbur will grow in non-sandy soil as well.
Range & Habitat: Sandbur is occasional to locally common throughout Illinois (see Distribution Map). It is more common in sandy areas. Habitats include sand prairies, sandy savannas, fields, areas along railroads and roadsides, lawns, and waste ground. Sandbur prefers areas with a history of disturbance; it is a rather weedy grass and is considered a nuisance in some areas.
Faunal Associations: The burs cling to animal fur and the clothing of humans; this helps to distribute the seeds across considerable distances. The sharp spines of the burs can easily penetrate the flesh; they can cause mechanical injury to the mouthparts of grazing animals and are painful to step on. Apparently, birds in Illinois make little use of the seeds. The ecological value of Sandbur to wildlife is low.
Photographic Location: A waste area along a railroad in Urbana, Illinois. Another species, Digitaria sanguinalis (Common Crabgrass), is present in the background of the photographs.
Comments: There is the only Cenchrus sp. (Sandbur) in Illinois, which makes the identification of this grass easy. Other species of Sandbur occur in sandy areas of the southeastern states. Another common name for Cenchrus longispinus is Matted Sandbur. The foliage of Sandbur and its habit of growth is quite similar to Digitaria spp. (Crabgrasses). Sometimes they even grow together in weedy lawns. However, Crabgrasses produce finger-like spikes of flowers that lack burs.