Muhlenbergia capillaris (Lamarck) Trinius. Hairgrass, Hair-awn Muhly. Phen: Aug-Dec. Hab: In the Piedmont and Interior Low Plateau primarily in clayey or thin rocky soils (especially in areas which formerly burned and were prairie-like) and in open woodlands; in the Coastal Plain in pine savannas, sandhills, dry woodlands, and coastal grasslands (where sometimes in close proximity with M. sericea); in the Mountains around calcareous rock outcrops; sandy prairies westwards. Dist: MA, NY, s. OH, s. IN, s. IL, MO, and e. KS south to s. FL, LA, and c. and s. TX; montane Mexico.

Origin/Endemic status: Native

Taxonomy Comments: M. capillaris and its relatives, M. expansa and M. sericea, were the subject of an herbarium morphological study by Morden & Hatch (1989), who concluded that the three taxa are not sharply separable and should be recognized only at the varietal level. If one considers behavior in the field, ecology, and geography in conjunction with morphologic characters, however, there is little doubt that the three taxa are biological species. Distribution and typical habitat are different for the three species, but M. capillaris can be found growing with or in proximity to each of the other two (I have not seen M. sericea and M. expansa together). In such situations, the two taxa present are readily distinguishable at a glance, and there is no evidence of intermediates or hybrids. Gustafson & Peterson (2007) also concluded that the three taxa are separable as species.

Synonymy: = Ar, ETx1, F, FlGr, FNA25, G, Il, K3, K4, NcTx, NE, NY, Pa, S13, SFla, Tat, Tn, Va, W, Gustafson & Peterson (2007); = Muhlenbergia capillaris (Lam.) Trin. var. capillaris – C, HC, K1, Mo1, S, WH3, Morden & Hatch (1989); < Muhlenbergia capillaris (Lam.) Trin. – GW1, Mex, RAB, Tx

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: FAC (taxonomic split from wetland indicator species)
• Eastern Mountains and Piedmont: FACU
• Great Plains: FACU (taxonomic split from wetland indicator species)
• Midwest: FACU (taxonomic split from wetland indicator species)
• Northcentral & Northeast: FACU (taxonomic split from wetland indicator species)

Heliophily: 8