D. purpurea and Digitalis lanata are the two economically important sources of cardiac glycosides. Both are biennial or perennial herbs growing in semi-shady regions in the wild state. Presently the leaves are collected from cultivated plants. D. purpurea is common in UK and most of Europe and naturalized in northern and western USA and Canada. Major centres of cultivation are Suffolk in UK, Wageningen in Holland and Pennsylvania in the United States. It is also grown in Egypt, Japan and India. D. purpurea has purple flowers with finger-shaped corolla.

D. lanata is indigenous to central and southeastern Europe and is cultivated in UK, former USSR, Ecuador and the United States. In Holland both the species of Digitalis are commercially cultivated. The plants generally resemble purple foxglove but the shape of the corollas is different and the pedicels are covered with woolly trichomes.

Leaves of other Digitalis species namely D. ferruginea, D. lutea, D. thapsi, D. grandiflora, D. mertonensis, D. nervosa, D. dubia, D. subalpina also show the presence of cardiac glycosides.