Flora of the Southeastern United States
2022 Edition

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Key to Sorghastrum

Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

1 Awns 10-22 (-30) mm long, once-geniculate; plants rhizomatous; surfaces of the glumes tan to slightly brown basally; ligule 2-10 mm long, prominently auricled
1 Awns 16-46 mm long, twice-geniculate; plants cespitose; surfaces of the glumes brown; ligule 1-5 mm long, truncate.
..2 Axis of the panicle straight, erect, the branchlets appressed to ascending, the spikelets drooping-secund; spikelets 0.8-1.2 mm wide
..2 Axis of the panicle arching, usually strongly so, the branchlets ascending to spreading, the spikelets not drooping-secund; spikelets 1.1-1.8 mm wide.
....3 Axis of the panicle straight, with the branches distributed no more than 180 degrees around the axis (as viewed from above); spikelets 1.3-1.8 mm wide; rachis 0.7-1.3 mm thick; flowering Jul-Aug.
....3 Axis of the panicle arching, with the branchlets distributed through 360 degrees around the axis (as viewed from above); spikelets 1.1-1.4 mm wide; rachis 0.3-0.8 mm thick; flowering Sep-Nov.