Any of several plants with red roots, such as the New Jersey tea (Ceanothus americanus), the gromwell (Lithospermum arvense), the bloodroot (Sanguinaria canadensis), and Lachnanthes caroliniana (syn. Lachnanthes tinctoria).
Sanguinaria canadensis, the bloodroot.
A plant used as a remedy for tetter, Chelidonium majus