- Name also: Common Comfrey, Common Comphrey
- Family: Borage Family – Boraginaceae
- Growing form: Perennial herb. Root juicy.
- Height: 30–120 cm (12–35 in.). Stem with soft or rigid hairs.
- Flower: Corolla campanulate (bell-shaped) (funnel-shaped or tubular), slightly constricted at tip, 5-lobed, 12–18 mm (0.48–0.72 in.) long, blue, dark or light purple, sometimes light red, yellowish or white, fused. Corolla lobes triangular, often slightly recurved. 5 large triangular protuberances in corolla throat. Calyx fused, deeply 5-lobed, 6–12 mm (0.24–0.48 in.) long, longer than calyx-tube. Calyx lobes sharp-tipped. Stamens 5. Gynoecium fused, single-styled. Axillary inflorescence a scorpioid cyme.
- Leaves: Alternate, stalked, usually widely decurrent. Blade lanceolate–ovate, base tapered, with entire margin, both sides hairy.
- Fruit: 4-parted schizocarp. Mericarps glossy, shiny, almost black, 5–6 mm (0.2–0.24 in.) long.
- Habitat: Yards, parks, meadows, roadsides, waste ground, shores, ditches. An escape and leftover from cultivation.
- Flowering time: June–September.
- Harmfulness: Potentially or locally harmful alien species.
Genus Symphytum is comprised of around 30 Eurasian members. Comfrey is known as an old ornamental and medicinal plant whose root has been used to help heal difficult wounds and broken bones. Its generic name means “to fuse” or “to grow together”, and one of its folk names is knitbone. Its Finnish name refers to the fact that it can survive in formerly inhabited places for decades. The plant has also been known in Finland by the slightly misleading name “blackroot”, ostensibly because of the root’s black surface, but it is not related at all to black salsify (Scorzonera hispanica), which is also known as blackroot. In Finland it has also been known as mucus-root on account of its white, slimy root, which certainly wouldn’t get anybody’s mouth watering. It is nowadays contra-indicated for internal use, even medicinally, because it contains carcinogenic compounds.
Comfrey’s other, reasonably common, relatives are prickly comfrey (S. asperum) and Russian comfrey (S. x uplandicum), which is a hybrid between comfrey and prickly comfrey. The species look quite similar. Perhaps the easiest way to tell them apart is to examine the form and length of the sepals’ lobes. In the comparative picture, comfrey on the left has long, narrow lobes; prickly comfrey on the right has short lobes, and Russian comfrey in the middle has medium-long lobes. The degree to which the leaves are decurrent and the form of the corolla also often help confirm classification.