1 Plants 0.4-1 m tall, relatively delicate, from creeping rhizomes, forming loosely tufted colonies; leaves 1-3 dm long, 1-3 mm wide, flat to channeled (terete apically), margins only slightly scabrous; inflorescence 0.5-3 dm long, of 2-4 umbelliform cymes, the branches rigidly ascending and bearing simple glomerules of spikelets; achene base squarely truncate to slightly flaring; [of Coastal Plain acidic seepages and tidal freshwater to slightly brackish marshes, Mountain fens or bogs]

1 Plants 1-3 m tall, coarse, from short rhizomes, forming dense tussocks; leaves 3-15 dm long, 5-12 mm wide, stiff and flat (or broadly V-shaped), the margins and midrib (beneath) harshly serrate (saw-toothed); inflorescence a narrow panicle 3-9 dm long, the branches bearing several fascicles of spikelets; achene base broadly rounded to truncate; [of tidal freshwater to brackish marshes, outer Coastal Plain calcareous savannas, freshwater marshes over limestone].

..2 Spikelets in clusters of 3-6; culms 1-2 m tall; inflorescences generally with only 3 orders of branching; [Edwards Plateau and immediately adjacent limestone areas, westwards and southwestwards]

..2 Spikelets mostly in clusters of 2-3 (-6); culms 1-3 m tall; inflorescences often with 4th order branching; [Coastal Plain, usually in coastal tidal marshes or inland but near-coastal over oolite or limesone]