Stems sparsely to densely hirsute. Leaves pilose. 2n = 32, 40, 48.

Flowering Aug-Oct. Open, often disturbed, dry to wet, sandy or rocky soils, prairies, old fields, sandy shores, bluffs and ridges, open deciduous woodlands, hammocks, roadsides; 0-1000+ m; B.C., N.B., N.S., Ont., Que.; Ala., Ark., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., Maine, Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., S.Dak., Tenn., Va., Wis.; introduced in Europe.

Variety pilosum is sometimes considered an agricultural weed (J. G. Chmielewski and J. C. Semple 2001b). It is introduced in British Columbia, New Brunswick, and Nova Scotia.

In southwestern Indiana this species is called goodbye meadow, which is a very appropriate name for it there because it soon forms dense stands in fallow fields and in meadows (hayfields). Frequent to abundant in all parts of the state in dry soil, in fallow fields, meadows, and open woodland and along roadsides. It should be regarded as an obnoxious weed because of its ability to crowd out other vegetation and because of its success in spreading widely by means of its wind-borne seed. It has a wide range of habitats, but is most at home in a clay soil. In good soil it reaches a height of over 3-4 feet, while a depauperate specimen growing in hard soil along the roadside may not be over a foot high. It is, also, rather variable. The involucres of my 40 specimens vary from 3.5-6.5 mm long. The bracts vary from 3-5 series. [Variety platyphyllus] was described by Torrey and Gray in the Flora of North America 2: 124. 1841, and they cite a specimen from Indiana collected by Dr. Clapp, who did his collecting in the vicinity of New Albany. It was also reported by Lyon from Porter County, and Peattie duplicated Dr. Lyon's report. I have seen this specimen and it is the common form of the species. This variety is described, in part, as follows: "Cauline leaves pubescent-hirsute, lanceolate; the lower ones oblong-spatulate", and with larger heads. I have specimens from Clark and Kosciusko Counties which I refer to this variety. These have leaves which are 20-30 mm wide. A specimen from Owen County approaches this variety, and my Jennings County specimen has a leaf 18 mm wide, while those of ordinary specimens are mostly less than 8 mm wide.