Grass family (Poaceae)
Description: This perennial grass is about 2-3' tall and unbranched. Each culm is green, slender, glabrous, and round in cross-section. The leaf blades are up to 8" long and 1/3" across; they are green, bluish green, or greyish blue, linear in shape, hairless, and rather flat. The sheath of each leaf is open and hairless; it has a tendency to split open into a deep-V shape, sometimes all the way to the node. The node at the base of each sheath is reddish or purplish and hairless.
The culm terminates in a panicle of one-flowered spikelets. This panicle is up to 10" long and half as much across; when fully open, it is broader at the base than at the top and rather airy in appearance. The pedicels of the spikelets are reddish or purplish and very slender. Each spikelet is 2-3 mm. in length; it consists of 2 glumes about 2-3 mm. long and a single fertile lemma about 1.5-2 mm. long. The glumes are keeled and lanceolate in shape; there are often small hairs or bristles along the edge of their keels, although this is difficult to see. While the flowers are blooming, the spikelets are light metallic red or light metallic purple; shortly afterwards, they become light grey and rather dull. The blooming period usually occurs from late spring to mid-summer for about 2 weeks. Upon maturity, the spikelets disarticulate above the glumes. The root system is fibrous and produces rhizomes or low stolons; Redtop is a sod-forming grass that forms dense vegetative colonies. It also readily reseeds itself.
Cultivation: The preference is full sun, moist to mesic conditions, and a loam or clay-loam soil. This grass adapts well to worn-out soil in agricultural fields.
Range & Habitat: Redtop is a common grass that can be found in every county of Illinois (see Distribution Map). It has a circumpolar distribution, occurring as a native grass in both North America and Eurasia. In Illinois, both native and introduced strains of this grass exist, although they are nearly impossible to distinguish from each other. Habitats include degraded prairies (especially clay prairies), moist meadows near streams, and fields. This grass is still used in agriculture as a source of forage (particularly for horses); it is often grown in SE Illinois for this purpose. Redtop is occasionally used in prairie restorations in southern Illinois, even though it probably isn't native to this area of the state. This grass prefers disturbed areas.
Faunal Associations: The wind-pollinated flowers attract few insects. The caterpillars of several skippers feed on the foliage of Redtop, including Amblyscirtes vialis (Common Roadside Skipper), Hesperia leonardus (Leonard's Skipper), Hylephila phyleus (Fiery Skipper), and the introduced Thymelicus lineola (European Skipper). The caterpillars of the moth Leucania pseudargyria (False Wainscot) feed on Agrostis spp. (Bentgrasses). The seeds are eaten by the Field Sparrow to a limited extent, while the Cottontail Rabbit occasionally browses on the foliage. Redtop is quite palatable to livestock.
Photographic Location: A moist grassy area along a drainage ditch in Champaign, Illinois.
Comments: Redtop is an attractive grass during its short period of bloom, otherwise it is rather ordinary looking. In areas where it is grown as an agricultural crop, it can become a significant source of hayfever during the early summer. Redtop can be distinguished from other Agrostis spp. (Bentgrasses) by its colorful inflorescence during the blooming period and the width of its leaf blades (up to 1/3" across). Other Bentgrasses have an inflorescence that is green or grey during the blooming period and their leaf blades are more narrow. Some spikelets of Redtop are located near the rachis (central stalk) of the inflorescence; the spikelets of other Bentgrasses are often more remote from the rachis. In general, Bentgrasses can be distinguished from other grasses by their tiny one-flowered spikelets and their keeled persistent glumes, which lack conspicuous tufts of hair. Redtop is often referred to as Agrostis alba, although this scientific name is considered obsolete by Mohlenbrock (1972/2002).