Porcupine Grass is a cool-season, clump forming, bunching grass, that has an erect non-branching stem (culm) growing from 1.5 to 4 feet tall. Lower stem nodes usually have lines of soft hair.
The leaves are very narrow, up to 3/16 inches wide, up to 15 inches long, flat to slightly convolute, rough on top, smooth and distinctly veined under.
Sheaths & Ligules. Leaf sheaths are usually smooth except the lower which usually have marginal hair. The ligules of lower leaves very small, 0.3 to 3.0 mm long, stiff and truncate, while the upper leaf ligules are longer 3 to 7.5 mm long, thin and acute. Auricles are absent.
Inflorescence: The grass becomes conspicuous when the large drooping flower heads produce seed. The inflorescence is a terminal panicle, 4 to 10 inches tall, (10 - 25 cm), not widely open or spreading, but nodding when heavy with seed.
Spikelets consist of just one floret, which is 15 to 25 mm long, with the two glumes longer (22 to 45 mm), but unequal in size. The lemmas have dense hair on the margins and lower portions (hair brown at maturity), but are smooth at the top ends. Florets have long awns, 90 to 190 mm long, usually crooked but straight at the upper end. The base of the floret is stiff and sharply tapered. (Awns are a bristle-like appendage which responds to changes in atmospheric moisture by coiling and uncoiling and by doing so ratchets and drills the very sharp point at the base end of the seed into the soil, thereby planting it.) Because of this sharp point at the floret base (and hence the name "porcupine grass"), anyone using it for forage should realize that when it matures, it is injurious to cattle. It can be an excellent choice to add texture and color to the home garden where soils are lighter and drier.
Habitat: Roots are fibrous. The normal growth range of this species is elevations of 200 to 2800 meters, usually on sandy soils in mesic to dry conditions.
Names: The genus name, Hesperostipa is derived from the words hesperis, meaning 'of the west' and stipa which refers to feather grass (derived from the Greek stuppē). The name was given to the Western Hemisphere grasses which resemble the Eurasian Stipa. The species name spartea, follows a similar logic, as it means 'like spartium in growth'. Spartium being Spanish Broom - a stipa. The older scientific name for this grass was Stipa spartea. The author names for the plant classification are as follows: First to classify it was ‘Trin.’ which refers to Carl Bernhard von Trinius (1778-1844), German botanist and physician who traveled extensively in Europe and Russia, studying botanical collections (even taught classes to the young Alexander II of Russia). His best known botanical paper was was on grasses, in 3 volumes, Species graninum. His work was amended by 'Barkworth’ which refers to Mary Elizabeth Barkworth (b. 1941) Agrostologist at the Utah State University, author of a number of papers on grasses, lead editor of the Manual of Grasses for North America, published by Utah State, and contributor to the grass section of Flora of North America.
Comparisons: There is a similar but smaller species, H. curtiseta, called Small Porcupine Grass, which has sheaths that are without hair, stem nodes that are either smooth or evenly hairy, and florets that are only 8.4 to 14 mm long. This species is known in Manitoba and the Dakotas, but the MN DNR does not yet report populations in Minnesota. H. comata, Needle-and-Thread grass is found in Minnesota - it has a more open panicle, shorter florets and longer awns.
Above and top left - A stand of Porcupine Grass. Photo ©Merel R. Black, Wisconsin Flora. Drawing above courtesy of NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. Manual of the grasses of the United States.
Below: 1st photo - The sharp tip at the base of the seed which works it's way into the soil by the twisting action of the large awn at the opposite end of the seed. Photo © Robert W. Freckmann, Wisconsin Flora. 2nd photo - detail of an upper leaf sheath, photo ©Anna Gardner, University of Iowa.
Below: Drawing of H. spartea with comparison to the similar H. curtiseta (see notes above). Drawing by Cindy Roché and Annaliese Miller ©Utah State University.
Porcupine Grass is a perennial native to the dry and moist prairies and plains within the central states from the Rocky Mountains eastward to the Great Lakes area and also to the lower central Canadian Provinces. In Minnesota it is found throughout the state except counties in the NE quadrant.
Two species of Hesperostipa have known populations in Minnesota: H. comata, Needle-and-thread grass; and H. spartea, Porcupine Grass. The former is more limited in range, found mostly in the western and southwestern counties of the state. The University of Minnesota states that it is probable that a third species, H. curtiseta, Small porcupine grass, may be found in the NW corner of the state where the state abuts known populations in the Dakotas and Manitoba.
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"