Indiangrass is a warm season grass, growing 5 to 7 feet in height on thick, erect stems (culms).
Leaf blades are up to 3/16 inch wide (4 - 6 mm - although some references will give width to 10 mm, that larger width is usually restricted to S. elliottii, Slender Indiangrass) and up to 27 inches (70 cm) long. They are flat, dull green to yellow-green, narrowed at the base, both upper and lower surface usually smooth.
Leaf sheaths are without hair except young plants may have fine white hair. Where the leaf sheath attaches to the stem, the ligule is 2 to 6 mm long, thick with pointed auricles, forming a distinct so-called "rifle-sight", even identifiable when the plant is young (see photo below).
Inflorescence: The seed head is a single narrow plume like panicle with many short branches, erect initially to slightly arching at maturity, and being up to 29 inches long in entirety, but usually in the range of 5 to 12 inches long. These appear dense because of the many short branches with whitish hair on the branch joints and on the sterile stalks (pedicels) that are paired with and subtended by the spikelet. In this species of Sorghastrum, the panicle is mostly equilateral in shape, not one-sided.
Spikelets are dark brown or golden brown when mature. They are 5 to 8.7 mm long, stalkless but subtending a hairy sterile stalk (pedicel) that has no spikelets. The terminal spikelet on the branch subtends two hairy pedicels. Glumes: The lower glumes are 5 to 8 mm long, have fine hair and 7 to 9 veins while the upper glumes are smooth with 5 veins, but the same length. The upper floret of the spikelet is bisexual, with whitish lemmas and awned. The lower floret is usually sterile and reduced to just a lemma. There are two anthers. The awns are 10 to 30 mm long (2 to 3 times the spikelet length) with one sharp bend. Seeds are very light, about 175,000 to the pound (or about 15,000 to the ounce).
Habitat: Indiangrass grows from short scaly rhizomes which can allow it to become invasive in certain habitats, but it makes excellent wildlife habitat and is a good forage plant. It frequently grows with Big Bluestem, which is similar in height. While it will grow in a wide range of habitats it requires full sun for best appearance, together with moist to mesic moisture conditions. This is one of the taller native grasses and in the landscape can be used for a mass effect. Cultivars are also available for the home landscape. The University of Minnesota Landscape Arboretum has had good success with "Sioux Blue".
Names: The genus Sorghastrum is derived from the word Sorghum, (a green corn-like plant) and the Latin astrum which means 'an imitation of' (usually a poor one) and together mean a similarity to the Sorghum plant. The species name nutans means nodding or drooping and refers to the position of the spikelet branches at maturity. The names of the authors for the plant classification are: '(L.)' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. He originally classified the plant and his work was updated by ‘Nash’ which refers to George Valentine Nash (1864-1921) American botanist who worked at the New York Botanical Garden.
Comparisons: There are three species of Sorghastrum found in North America, S. secundum, Lopsided Indiangrass; S. elliottii, Slender Indiangrass; and S. nutans, usually known only as Indiangrass, but only the latter is found in Minnesota. S. nutans is distinguished from the other two by being rhizomatous and having awns with only one bend. If the panicle has branches all to one side (said to be 'secund') and the awns are twice bent, 21 to 40 mm long (twice the length of S. Nutans), then it is S. secundum; but if the panicle is equilateral like S. nutans and the awns are with 2 bends, then it is S. elliottii. See diagram below.
Above: A stand of Indiangrass in the Garden. Photo ©Phoebe Waugh. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions.
Below: The panicle of Indiangrass. 1st photo - - at mid-August, 2nd photo - in October.
Below: 1st photo - The panicle approaching maturity and 2nd photo - The whitish hairs on the pedicels make the panicle appear dense. Note the awns with one major bend projecting from the spikelets.
Below: The spikelets of Indiangrass subtend a sterile hairy stalk (pedicel); glumes have fine hair and there is a twisted awn that is 2 to 3 times the length of the spikelet. The spikelet, pedicel and branch disarticulate as a unit.
Below: 1st photo - View of the stem, sheath and ligule. Note the narrowing of the blade as it approaches the stem. 2nd photo - The characteristic "rifle-sight" stem ligule of Indiangrass, seen best in the early growth stage.
Below: A comparison drawing of the three species of Sorghastrum by Linda A. Vorobik and Annaliese Miller., ©Utah State University.
Below: Indiangrass and Big Bluestem growing together in the Upland Garden in August.
Notes: Indiangrass is indigenous to the Garden. Eloise Butler catalogued it in her early Garden records; for example noting it in bloom on Aug. 21, 1914. Cary George reported planting it in 1995.
Indiangrass is native to the entire U.S. and lower Canadian Provinces from the Rocky Mountains eastward. In Minnesota it is generally found in most counties except those of the NE Quadrant. It was once one of the major plants of the tall-grass prairies that covered much of the central and eastern United States.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"