Phaeocephalum dodecandrum (Baldwin ex A. Gray) House; Rhynchospora dodecrandra Baldwin ex A. Gray; R. pycnocarpa A. Gray

Plants perennial, cespitose, to 130 cm, coarse; rhizomes scaly, stoloniferous, stout. Culms erect to arching, leafy, trigonous, slender, firm. Leaves overtopped by culms; blades linear, proximally flat, 3–7 mm wide, apex trigonous, subulate, tapering. Inflorescences: spikelet clusters 2–6, sparse, widely spaced, turbinate; peduncles and branches ascending; leafy bracts exceeding proximal clusters. Spikelets light red brown, ovoid to ellipsoid, (4–)5–8(–9) mm, apex acute or acuminate; fertile scales ovate, (5.5–)6–6.5(–7) mm, midrib included or short excurrent. Fruits 1–2 per spikelet, (3.5–)4–5 mm; body dark brown to mahogany or nearly black, broadly obovoid, tumid, nearly smooth, buttressed to tubercle; tubercle low conic, rimmed, 0.7(–1) mm, apex apiculate. Flowers: perianth bristles 6(–8), mostly reaching from fruit midbody to tubercle base, antrorsely barbellate.

Fruiting summer–fall. White or yellow sandhills; 0–300 m; Ala., Fla., Ga., Miss., N.C., S.C.

The perianth in Rhynchospora megalocarpa is unusual. The receptacular joint is stubby, bearing staggered cycles of bristles that vary extremely in length and number—on a par with R. alba, R. baldwinii, and R. macra in numbers of bristles. The greatest extreme is twelve, the fewest as low as two; usually if the number is low, the remaining sites for bristles will be dark-colored nubbins.