This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Perennial. Propagates by seed. Time of bloom: June to September. Seed-time: Late July to November. Range: New England States, southward to New Jersey. Habitat: Fields, pastures, and waste places.
An immigrant from Europe not yet very widely disseminated in this country. Stems, several from the same thick, woody, branching root, erect, stiff, grooved, slender, one to two feet in height, branching near the top. Leaves narrowly lance-shaped, the lower ones sparsely toothed and tapering to a petiole, the upper ones entire and sessile. Heads showy, an inch or more broad, with rosy purple corollas, all tubular but the outer row with enlarged and lengthened lobes, simulating rays; these showy florets are sterile; involucres nearly globose, the bracts closely imbricated, glossy dark brown, the outer row fringed, the middle ones slightly lacerate, the inner ones entire or nearly so. Achenes four-sided and without pappus.
Prevent seeding by cutting while in early bloom, and, if the area infested is small and the plants are not too numerous, grub out or hand-pull the perennial roots when the ground has been softened by rain. Otherwise they may be destroyed by putting the land under cultivation.