Comfrey petals. Coloured scanning electron micrograph (SEM) of the petals of a comfrey (Symphytum officinale) flower. Comfrey is a perennial herb with large, prickly leaves and pink or cream bell-shaped flowers. It grows wild in North America and is cultivated in many countries for its supposed medicinal properties. The leaves and roots are believed to be able to treat fever, inflammation, wounds and broken bones. However, taking it by mouth can be dangerous due to the presence of pyrrolizidine alkaloids which can cause liver damage. Magnification: x100 at 6x7cm size.