This robust variety is a relatively aggressive weed in corn and bean fields, especially in the midwest, where it often rivals faberi. It was unknown in Ky. until colls. of P. Haragan and others during 1980-2000 (KY, EKY). Var. robusta-purpurea Schreib. differs only in the purplish coloration of its spikes, and is not segregated here.