Mexican Muhly Grass is a perennial native rhizomatous grass with erect stems, much branched above the base, growing 1 to 3 feet high. Stems nodes are dull and vary from smooth to having extremely small hairs.
Leaves: Leaf blades are flat, to 8 inches long and narrow (to 1/4 inch wide), either smooth or with a rough surface. Leaf blades on secondary branches are the same length and width as on the main branches.
Sheaths & Ligules: Sheaths are open, usually smooth and somewhat keeled (like a boat hull). Ligules are truncate and membranous, 0.4 to 1 mm long.
The Inflorescence is a flowering spike-like panicle that forms either terminally or on side branches and is up to 8 inches long but just over an inch wide. The primary branches of the main panicle are thus quite short, usually appressed to the rachis or spreading up to 30 degrees. Any axillary panicles are on long stalks.
Spikelets: The flowers are green but not conspicuous. Spikelets are often purple tinged and only 1.5 to 3.8 mm long. There is usually only one floret per spikelet; the glumes are sub-equal, 1.5 to 3.7 mm long with one vein, the glumes may be awned and if present, are only 2mm long. The lemmas are about the same size as the glumes, 1.5 to 3.8 mm long, veined and generally with hair on parts. They also may be awned and if so, awns are up to 10 mm long. There are 3 anthers to the florets, yellow to purplish in color.
Varieties: Two varieties are recognized: Var. filiformis where awns are 3 to 10 mm long, and var. mexicana which either is awnless or with awns less than 3 mm long. Both varieties are found in Minnesota.
Habitat: Mexican Muhly Grass grass prefers full sun but will tolerate shade, but requires a moist soil such as along stream banks, ditches, swamps, marshes, and moist prairies. It is not a long-lived plant. Like most of the Muhlenbergia genus, it grows by rhizomes and thus can form colonies, but does not form clumps. It can cross with the other Muhlenbergia in the Garden, M. racemosa. While palatable to grazing animals, it is not an important forage grass.
Names: The genus name, Muhlenbergia, is an honorary for Gotthilf Heinrich Muhlenberg (1753-1815) a U.S. citizen and German educated botanist who produced several catalogues of plants after retiring as a Lutheran pastor. The species name, Mexicana means 'of Mexico' and despite that name it grows only in the United States and Canada and usually far from Mexico. The author names for the plant classification are: First to classify was ('L.') which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was amended by ‘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 on grasses, in 3 volumes, Species graninum.
Comparisons: The species most closely resembling M. mexicana is the Nodding Muhly, M. bushii, which is found in the midsection of the United States, overlapping the range of M. mexicana. With M. bushii, the axillary panicles are poorly developed, stem nodes are shiny not dull, and leaf blades on secondary branches are shorter and more narrow than on the main branches. A drawing comparing the details of the two Muhlenbergia species found in the Garden is shown below - M. mexicana and M. racemosa.
Above: A stand of Mexican Muhly Grass. Photo ©Emmet J. Judziewicz, University of Wisconsin. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions.
Below: 1st photo - stem detail, note the almost microscopic hair on the node. 2nd photo - A group of spikelets, each with a single floret. Note the long lemma awn. Both photos ©Anna Gardner, Iowa State University.
Below: A drawing comparing the details of the two Muhlenbergia species found in the Garden. Drawing by Linda A. Vorobik and Annaliese Miller, ©Utah State University.
Mexican Muhly is indigenous to the Garden. Eloise Butler catalogued it on May 31, 1907. It is found in scattered populations in many states of the United States but its main range is from Minnesota, Iowa and Missouri on the west, then eastward to the coast. In Minnesota it is found in most counties of the state but with many exceptions in the dryer SW Quadrant.
It is one of ten species of Muhlenbergia found in Minnesota. One other was reported, but never collected. Only two of those ten species, M. racemosa, Marsh Muhly, and M. mexicana are found in the Garden.
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"