Paspalum is a short-lived, warm-season, tufted perennial that grows from short rhizomes. The round stems may be erect or spreading with few stems in a tuft, growing from 10 to 40 inches high. The stem nodes may be hairy, particularly at the leaf sheath collar.
Leaf blades are flat and either mostly basal and recurved (2 varieties) or more evenly distributed and lax to straight (7 varieties). Blades are 2 to 10 inches long and up to 6/10 inch wide.
Sheaths and collars: The leaf sheaths may have some fine hair, ligules are short - 0.2 to 0.5 mm long.
Inflorescence: The flowering seed heads are terminal and axillary panicles with 1 to 6 branches arranged as racemes, but usually only 1 to 3 per stem, and each is from <1 to 5 inches long. Initially they are enclosed by the leaf sheath and then enlongate. Axillary panicles are usually solitary and usually partially to completely enclosed by the leaf sheath.
The spikelets are usually in pairs, arranged alternately in two rows on one side of the flattened raceme and appressed to the rachis. They are straw to brown in color, each spikelet is 1.4 - 2.6 mm long. The lower glumes are absent, the upper glume is 3-veined as is the lower lemma, but the lower lacks ribs on the veins. Both usually have fine hair. Upper florets in the spikelet are bisexual and straw color. Lower florets, if present, are sterile.
Habitat: Paspalum prefers sandy soil and is typically found in open woods, open ground, old fields and wood borders. It is not aggressive or a prolific plant as seed production and germination is low. This is a good example of a native grass that should be part of any prairie restoration, but low seed production limits its ability to provide a good wildlife seed source or its ability to maintain the population.
Names: The genus Paspalum comes from the Greek paspalos, referring to a type of millet. The species name, setaceum, means 'bristled'. The author name for the plant classification - ‘Michx.’ refers to Andre Michaux (1746-1802), French botanist who made many exploring expeditions in the U.S. collecting and cataloging many species. Two important works were the Histoire des chênes de l'Amérique septentrionale (1801 - Oaks of North America), and the Flora Boreali-Americana (2 vols., 1803, published posthumously). His son Francois, traveled with him and the father’s notes were later used for the 3-volume North American Sylva, for which Thomas Nuttall provided some supplements.
Comparisons: Varieties: Nine varieties are found in North America, distinguished by having either basal, recurved leaf blades (2 varieties) or blades more evenly distributed (7 varieties). Two varieties are reported by the U of M Herbarium as being within Minnesota; both are in the second group and are erect to spreading plants, not prostrate and can have fine blade surface hair and marginal hair on the blades: Var. muhlenbergii (Nash) D.J.Banks has lower lemmas with evident midveins, are usually without hair and light green to green; var. stramineum (Nash) D.J.Banks, is possibly in the state, has leaf blades that are yellowish-green to dark green, either completely smooth or conspicuously hairy and lower lemmas without evident midveins.
Above: 1st photo - Two branches of the panicle of Paspalum. Photo ©Aaron Carlson, Wisconsin Flora. 2nd photo - detail of sheath and blade, Image is of of var. stramineum. Photo ©Anna Gardner, Iowa State University.
Below: Drawing of 4 variations of P. setaceum including var. muhlenbergii which is found in Minnesota. Drawing ©Linda A. Vorobik and Cindy Roché, Utah State University.
Below: Detail of the panicle showing the alternate arrangement of spikelets along the two rows subtended from the raceme. Image is of of var. stramineum. Photo ©Anna Gardner, Iowa State University.
Below: Mature seed - photo ©Jose Hernandez USDA-NRCS Plants Database
Paspalum is a native grass is found in the United States in the eastern 2/3 rds of the country, from the Great Plains east to the coast but with spotty distribution within individual states. In Minnesota it has been found in only ten counties - all from the metro area south along the river corridor. There are nine recorded varieties that have varying distributions within the states. Two varieties are reported by the U of M herbarium as being within Minnesota: Var. muhlenbergii (Nash) D.J. Banks and possibly var. stramineum (Nash) D.J. Banks, although it has not been collected. These are the only species of Paspalum found in Minnesota.
In North America there are 43 species of Paspalum of which 24 are native.
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"