Biennial or sometimes perennial, 6-18 dm; cauline lvs lanceolate to lance-ovate, gradually tapering to the base, crenate, hairy beneath; sep 10-15 mm, overlapping, the largest broadly elliptic to obovate; cor 4-5.5 cm, narrowly campanulate, purple or white, spotted with dark purple inside; 2n=56. Native of Europe, occasionally escaped from cult. in our range. Summer. Classical source of the drug digitalis.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.