Common foxglove (Digitalis purpurea), also foxglove, cinquefoil, foxweed, a poisonous plant, species of the genus foxgloves, Digitalis, in the plantain family, long known in folk medicine as a remedy for heart failure, cardiac insufficiency, and has been used medicinally since the late 18th century. species of the genus foxgloves, in the plantain family, long known in folk medicine as a remedy for heart failure, cardiac insufficiency, and has been used