Blue Grama grass is a major warm season perennial tufted grass, growing 1 to 2-1/2 feet in height on slender stems (culms).
Leaf blades are very narrow, up to 0.1 inch wide (1 to 3 mm) and 1 to 6 inches (15 cm) long. Most grow near the base of the plant. They vary from flat to rolled, (rolled generally where they emerge from the sheath and near the tip) with tips that are usually wavy to curly. They are a medium green color with a bluish tint, with the upper surface somewhat rough and the lower surface less so or even smooth. Blade veins are parallel and distinct. Where the leaf sheath attaches to the stem it is split and the throat is slightly hairy and the ligule has dense short hairs. Auricles are absent.
The flowering stem is a panicle with 1 to 3 branches on the stem. Spiklets are on these branches, forming a raceme-like structure, held outward from the stem. These are usually curved, about 3/4 to 3-1/4 inches long and densely flowered, but only on one side of the raceme rachis with a single spikelet at the tip. They appear dense and comb-like with 40 to 130 spikelets per branch. Spikelets are paired with one sterile and one perfect. Anthers may be yellow (as shown below) or purple. At maturity the racemes curve resembling a human eyebrow, hence the alternate common name.
Seeds are very light, about 40,000 to the ounce and have three awns attached. (Awns are bristle-like appendages at the tip of the seed that can make a twisting response to temperature and humidly changes and thus help the seed to work into the soil). Seeds are capable of germinating in warm conditions as soon as mature but if they must be stored, storage should be dry cold storage.
Habitat: Blue Grama grows in bunches due to the fibrous root system producing small short underground tillers and by re-seeding. The species has good drought tolerance, will tolerate partial shade, but prefers mesic to dry conditions. In cool climates it can form sod and is sometimes used in grass mixtures.
Names: The genus Bouteloua is an honorary for Claudio and Esteban Bouteloua, 19th century Spanish botanists who studied grasses in the new world. The species, gracilis, means 'thin' or 'slender' referring to the thin stems. The plant classification authorship is much involved. First to work on the species, ‘Kunth’ refers to Carl Sigismund Kunth (1788-1850) German botanist, the first person to study and categorize plants from the Americas, publishing 7 volumes about same. Later work was done by ‘Lag.’ which refers to Mariano Lagasca (1776-1839) Spanish botanist, professor of botany at the University of Madrid and director of the Royal Botanical Garden of Madrid. Final work was done by ‘Griffiths’ which refers to David Griffiths (1867-1935) American botanist and plant collector who eventually worked for the U.S. Dept of Agriculture in the office of Grass and Forage Plant Investigation. In earlier times the plant was classified as Bouteloua oligostachya.
Comparisons: A very close relative is Hairy Grama which has patchy hair on the blades and a projection at the tip of the flowering head that is lacking in Blue Grama. Side-oats Grama, B. curtipendula, has the spikelets much more spread out and not comb-like.
Above: Blue Grama is a tufted grass growing 1 to 2-1/2 feet high. Flowering heads number 1 to 3 on a stem. Drawing by Hitchcock, A.S. (rev. A. Chase). 1950. Manual of the grasses of the United States. Courtesy USDA Plants-Database.
Below: A dense tuft showing many maturing seed heads in late summer. The leaf blades have numerous distinct parallel veins.
Below: Two views of the sheath and ligule. The sheath at the attachment point to the stem is split and the ligule has short dense hairs. No auricles.
Below: At flowering time - there are 40 to 130 spikelets per head. They are paired - one sterile and one perfect. The pendulous anthers of this specimen are yellow but may be purple.
Below: The mature seed head showing the projecting awns from the spikelets. This curvature is typical and led to the alternate common name of 'eyelash grass'.
Blue Grama is not indigenous to the Garden or to Hennepin County. Eloise Butler introduced it to the Garden in 1912; she noted obtaining it from Columbia Heights but it is not known to be native there, but maybe it was in 1912. She may also have obtained it from a nursery there. She used the older name Bouteloua oligostachya which today is considered a synonym for B. gracilis. It is no longer extant in the Garden.
Blue Grama is a native prairie grass found in about 1/3 of the counties in Minnesota, principally in the western half of the state with a few scattered remnants in eastern counties such as Winona, Ramsey and Dakota (which are the only two metro counties known to have it today). In North America is found mostly in the western 2/3rds of the continent, extending eastward around the Great Lakes and then the lower Canadian Provinces from Ontario westward. There are three species of Bouteloua native to Minnesota: B. curtipendula, Side-oats Grama; B. gracilis, Blue Grama; and B. hirsuta, Hairy Grama.
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"