Petasites hybridus

Butterburs are tall perennials of the subfamily Asteroideae. They are dioecious, which means that there are separate male and female individuals. Butterburs have flowering stems that emerge in late spring, and grow taller at the fruition stage. At the final stages of flowering, green rosette leaves emerge from the ground. They grow over the summer to become up to one metre wide. Butterburs spread vegetatively from rhizome fragments.Common butterbur usually has deep purple flowers. In Finland, the plants are almost exclusively male. Japanese butterbur (P. japonicus ssp. giganteus) has yellowish flowers and only male plants exist in Finland, and throughout the Nordic countries. None of the species produce seeds in Finland.