Prairie Wedge Grass
Sphenopholis obtusata
Grass family (Poaceae)

Description: This perennial grass is 1-3' tall, forming a small tuft of unbranched culms with alternate leaves. The slender culms are light green to straw-colored, terete, and glabrous. About 3-4 leaves occur along the lower two-thirds of each culm during the blooming period (see Culms and Leaves). The leaf blades are up to 5 mm. across and 5" long; they are ascending to spreading, dull green, flat, and either hairless or short-pubescent. The open leaf sheaths wrap tightly around the culms; they are dull green, longitudinally veined, and either hairless or short-pubescent. The nodes along each culm are swollen, purple-tinted, and hairless, while the short ligules are papery-membranous. Each fertile culm terminates in a narrow erect inflorescence about 2-6" long, consisting of a spike-like panicle. An immature inflorescence is whitish green, becoming tan at maturity. The lateral branches of the inflorescence are up to 2" long and erect to ascending. Each spikelet of the inflorescence is 2.5–3.5 mm. long, consisting of a pair of glumes, 2 lemmas (rarely 3), and their florets. The first glume is linear-lanceolate, while the second glume is obovate and slightly longer than the first glume. The glumes are 2-3 mm. long; they are green-veined in the center, white along their margins, and occasionally purple-tinted. The rather broad apex of the second glume is rounded to nearly truncate. The lemmas are 2-3 mm. long and largely hidden by the glumes. The blooming period occurs from late spring to mid-summer. Each floret has 2 plume-like stigmata and 3 anthers. The root system is fibrous. This grass spreads by reseeding itself.

Cultivation: The preference is full to partial sun, mesic conditions, and soil containing loam, clay-loam, or some rocky material. Most growth and development occurs during the spring and early summer.

Range & Habitat: The native Prairie Wedge Grass is occasional throughout Illinois (see Distribution Map). Habitats include mesic prairies, thinly wooded bluffs, open rocky woodlands, and pastures. Prairie Wedge Grass is found in prairies to a much greater extent than other Sphenopholis spp. (Wedge grasses). It is rarely abundant in any one location.

Faunal Associations: Very little is known about the floral-faunal relationships of Prairie Wedge Grass and similar species. The foliage is edible to horses, cattle, and other livestock.

Photographic Location: The Loda Cemetery Prairie in east-central Illinois.

Comments: This prairie grass superficially resembles one of the weedy species of grass. It is easy to overlook, except during the blooming period, when its inflorescence rises above the surrounding vegetation for a short period of time. Across its range, there is some variability in the size of individual plants, the presence or absence of pubescence, and the extent to which the inflorescence is contracted into a spike-like panicle. Prairie Wedge Grass can be distinguished from other Sphenopholis spp. (Wedge grasses) by its more contracted and spike-like inflorescence and its rather broad obovate second glumes. The lateral branches of other Wedge grasses are more divergent (usually ascending) and their second glumes are more narrow. At one time, Sphenopholis intermedia (Slender Wedge Grass) was considered a variety of Prairie Wedge Grass, but it is now classified as a distinct species.