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1 Mature perianth with one basal tubercle or spine, rarely absent; leaf blades (at least the distal ones) ovate-orbicular or short oblanceolate; spikelets dense, flowers arranged in a 5-ranked spiral (viewed from apex); plants perennial
..2 Mature perianth slightly oblique apically, with irregularly and deeply cut (‘‘spiny’’) lateral wings; flowers 2.4-3.8 mm long; stems slender, branched from base (except in depauperate specimens with only 1 slender stalk); floral spikes 3-ranked; bracteoles glabrous, not pubescent distally; stem pubescence grayish-white
..2 Mature perianth symmetrical, with irregularly dentate to crenulate lateral wings; flowers 3.5-6 mm long; stems stout with one or more erect to decumbent branches from ground level; floral spikes 5-ranked (rarely 3-ranked); bracteoles glabrous to sparsely or densely pubescent distally; stem pubescence grayish-white or brownish.
....3 Interstaminal lobes blunt, brown-tinted (often observed as darkened flower tips), 0.5–0.7 mm long, usually not recurved; bracteoles sparsely hairy distally; flowers 3.5–5.4 mm long; [sc. TX]
......4 Leaf blades orbicular to broadly elliptic, abaxial surface of leaves densely wooly; [s. TX, principally coastal]
........5 Hairs of the peduncles < 0.5 mm long; plants typically 3-10 dm tall; [of w. KY Mississippi Embayment westward]
........5 Hairs of the peduncles mostly 1-2 mm long; plants typically 10-20 dm tall; [of the Southeastern Coastal Plain]