1. Sessile florets with body (5-) 6-9 mm long and awn tightly twisted basally; stalked floret rudimentary or well developed and staminate; base of at least some racemes usually exserted at maturity; ligule of major culm leaves ca. 0.9-2.5 mm long; stamens 3, the anthers (2-) 2.5-5 (-5.5) mm long.

A. gerardii

1. Sessile florets with body ca. 3-3.5 (-4) mm long and a straight awn; stalked floret usually represented by only a hairy pedicel; base of racemes ± included in spathe-like leaf base even at maturity; ligule of major culm leaves a minutely ciliate scale ca. 0.5-0.6 mm long; stamen 1, the anther not over 1 mm long.

A. virginicus