Nearly inodorous; stems 5-8 dm, very leafy, with many short axillary branches; herbage glabrous; lvs linear, entire, those of the main axis 2-5 cm נ2-4 mm; lateral veins 1-2(3) pairs, all arising in the basal fourth of the lf; heads very numerous and dense, hemispheric 3-8 mm wide, on peduncles 3-15 mm; outer bracts lanceolate, sometimes surpassing the heads; inner bracts numerous, closely appressed, about as long as the cals, firm, lanceolate, long-acuminate, the conspicuous midvein produced into a stiff, subulate point; cal-lobes narrowly triangular, acuminate, puberulent, usually 1-1.5 mm; cor 5-8 mm; 2n=80. Chiefly in dry soil of upland woods and prairies; Me. to Fla., w. to Minn., Kans., Okla., and Tex. (P. flexuosum, misapplied; P. linifolium)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.