Comfrey (Symphytum officinale) is a perennial herb in the Borage family native to Europe and now found growing wild throughout America. Historically, comfrey was used as to heal wounds and broken bones, leading it to be alternately referred to as knitbone or bruisewort. The ancient Greek physician Dioscorides suggested it for this purpose in the 1st century. In recent times, however, comfrey has been found to contain pyrrolizidine alkaloids, known to cause liver damage in high doses.
Comfrey and foxglove
An even greater danger than its toxic alkaloid content is comfrey's close resemblance to foxglove (Digitalis purpurea). Foxglove can kill if ingested, causing fatal heart irregularities and palpitations. Therefore, when harvesting comfrey in the wild, it is imperative to ascertain that it is indeed comfrey and not its deadly lookalike which is being collected.
The most noticeable difference between foxglove and comfrey is the size and shape of their flowers. Comfrey flowers emerge in nodding clusters in late spring or early summer. These flowers are small, delicate and bell-shaped. They may be creamy white, light yellow, red, purple, pink or blue in colour. Like comfrey blossoms, foxglove flowers hang downward. These trumpet-shaped blooms, however, are much larger and showier than those of comfrey. They are pinkish-violet in colour and bear distinctive white and purple spots on the inside of their petals.
Comfrey leaves die off in the winter, re-emerging each spring in thick bunches 90 cm (3 feet) in both height and diameter. From the centre of the dense cluster, a stalk bearing alternating leaves ascends, ultimately bearing flower clusters at its apex. The leaves themselves are long and pointed, with deep veins radiating from a prominent central vein which bisects each leaf. They mature to a deep emerald hue. Comfrey leaves can reach lengths of 45 cm (1 1/2 feet). They are covered in short, scratchy hairs, giving them a sandpapery texture.
Comfrey roots grow in a wide-spreading, branching pattern, establishing the plant firmly in the soil and making it difficult to uproot. These roots are brittle in texture. On the outside, they are a deep, chocolate shade of brown. When broken, they reveal a creamy white colour inside and a fresh, bright scent.
Like its cousin borage, the fresh leaves of the comfrey plant emit a crisp, clean aroma similar to that of freshly sliced cucumbers. This distinctive smell is yet another way in which comfrey can be identified in the wild.