This biennial weed from Europe and northern Africa is the common wild "teasel" that is widely naturalized in humid, mid-temperate regions of North America. It was probably present in Ky. early after settlement (Rafinesque 1836), but Gray (1864) noted "rather rare" in northeastern states. In 1914 for Ky., Gm just noted "not so often seen in cultivated ground." It is now locally abundant in the state, especially along major roads on more fertile soils, as in the Bluegrass region. D. fullonum has well-developed perfoliate "cups" at its paired leaf bases. Recent research has supported an early hypothesis of Charles Darwin that nutrients from dead insects in the water of these containers can increase fitness of the plant. Shaw & Shackleton (2011) showed that addition of insects can increase seed set by ca. 30%, though not the overall biomass. Species with less pronounced perfoliate to connate leaves include Triosteum perfoliatum, Smallanthus uvedalia, Silphium perfoliatum and Eupatorium perfoliatum. But these species do not generally collect water and insects. The name fullonum has been misapplied to D. sativus (L.) Honckeny, which differs in its more spreading involucral bracts (versus curved upward) and more rigid recurved receptacular bracts (versus straight); its flowers tend to be larger (tubes ca. 13 mm versus 9-11 mm) and perhaps paler pink to whitish (versus usually pink-purple). D. sativus is at most a subspecies or cultivar, selected in Europe for processing of textiles (Clapham et al. 1962, Ryder 1994). Rarely naturalized in North America (F, Cr, W, K), it is reportedly common in some parts of Hamilton Co. and elsewhere in s. Ohio (PL; D. Boone, pers. comm.), but it has not been verified in Ky. These Ohio plants may be hybrids with D. laciniatus.