This widespread dioecious perennial alien weed, with creeping roots, was first reported from Ky. about 1900. In 1914 Gm noted: "has of late overrun the cultivated land of Kentucky. It has been introduced in large quantities with clover and other seeds [including bluegrass], and it is being scattered still further with several of our small-seeded forage plants." However, it is not now a serious agricultural or horticultural weed. Within lawns or other grasslands, it is largely restricted to patches of bare or rocky ground on relatively infertile soils; dense growth of fescue, bluegrass or other common turf-forming grasses generally exclude this species. See FNA 5 for notes on variation; North American plants are generally referable to the hexaploid ssp. pyrenaicus (Pourret ex Lapeyrouse) Akeroyd.