D. purpurea is a common ornamental plant of England well known for its medicinal properties. Horticultural varieties grown as garden plants are low in therapeutic glycosides. For pharmaceutical purposes, cultivation is preferable to collection from wild plants because factors such as the climate, soil, age of the plant, season, storage and drying method and genetic makeup of the cultivated strain influence the activity of the drug. The plants are cultivated from the seeds and produce a rosette of leaves in the first year. The first crop of leaves is collected, and the next year the flowering stems which begin to appear are cut off to encourage further leaf growth, which are again collected in the second year. The plants may thus continue to yield a crop of leaves for several years in succession. However total glycoside levels are higher in first-year leaves and medicinally important glycosides are highest in the second-year leaves. Hence the first- and second-year leaves are to be collected as per the pharmacoepias. The leaves have to be collected in dry weather and dried as quickly as possible in the dark at temperatures between 55 and 60° C, since moisture and higher temperatures activate enzymatic degradation of the active glycosides into inactive forms. The dried leaves are to be stored in moisture-free containers and should not contain more than 5% moisture.