Plants 2-8 dm. Leaf blades lance-olate to obovate-lanceolate, oblong, or elliptic, 3-11 × 1-3(-3.5) cm, lengths mostly 2-7 times widths, margins usually dentate or denticulate, slightly repand, sometimes nearly entire. Heads in dense, usually continuous, rarely interrupted (then near bases), narrow, ± ovoid arrays (2-)3-8(-10) cm (usually single, sometimes with 1-2 basal branches). Involucres campanulate, 4-5 mm. Pistillate florets 23-44. Functionally staminate florets 6-10(-15). Cypselae 1-1.3 mm. 2n = 20. Flowering May-Jun. Sandy pinelands, sandy fields, depressions, ditches; 0-20 m; Ala., Fla., Ga., Miss., N.C., S.C. Differences between Pterocaulon pycnostachyum and P. alopecuroides (Lamarck) de Candolle, which is widespread in the West Indies and South America, are these: plants 50-70 cm high in P. pycnostachyum (versus 70-150 cm in P. alopecuroides), arrays of heads 4-8 cm (versus 3-17 cm) long, involucres 3.5-4 mm (versus 4.5-5 mm) high, and 6-15 (versus 1-3) functionally staminate florets (A. L. Cabrera and A. M. Ragonese 1978). In P. alopecuroides, the arrays of heads are almost always interrupted proximally, commonly producing sessile to subsessile branches. A count of functionally staminate florets provides a clear determinant for plants that might appear ambiguous in other features.