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In mesic morainal oak woodland associated with northern flatwoods

Perrennial, from rhizomes with short internodes. Culms round, lax, freely branching, glabrous and shiny below the nodes. Although the nodes are minutely roughened right below the base, especially on the lower nodes. Blades of main branches up to about 5mm wide, flat at maturity. Blades of axillary branches shorter and narrower than on main branches. Ligules about .5mm. Terminal panicles very narrow, with short, strictly appressed, ascending branches. Axillary panicles abundant, partially included in sheaths. Glumes subequal, about 1/2 to 2/3 as long as the pubescent lemmas (excluding awns), lanceolate to narrowly ovate, without awns or with awns less than 1mm, less than 2 mm long.

Muhlenbergia frondosa is most similar with smooth shiny culms, partially included axillary panicles, and similar habit. But it is a more robust plant with larger glumes, panicles, and ligules.

This is an extremely unusual find if I have identified it correctly. M. bushii is only known from the Kankakee region of Chicago. But this keys very easily to M. bushii in Flora of North America and Flora of the Chicago Region. For Muhlenbergia species in the Chicago Region, M. asperifolia, M. cuspidata, M. richardsonis, M. schreberi, M. glomerata, M. racemosa, and M. glabrifloris are easily ruled out based on unmistakable morphological differences. M. frondosa has already been discussed. M. sobolifera and M. tenuiflora can be confused with M. bushii based on their gracile habit and inflorescences, and if the glumes here are interpreted as being more distinctly ovate. Those species are more erect, less branched, and with mostly terminal and exserted panicles. M. tenuiflora also has distinctly pubescent culms. And M. sobolifera has glumes about as long as the lemmas which have awns up to 1mm. M. mexicana and M. sylvatica could be confused with M. bushii based on the abundant branching, and if the culms here are interpreted as being puberulent but with the pubescence worn off. However, these species have exserted axillary panicles and lance-attenuate glumes about as long as the lemmas. M. mexicana also typically has wider terminal inflorescences. M. sylvatica has narrower panicles but ligules 1-2.5mm long