Comfrey (Symphytum officinale)

Comfrey (Symphytum officinale) is a wonder plant. It is a dynamic accumulator, drawing minerals out of the soil and into the roots and leaves, a compost accelerator, a fine ingredient in liquid manure (comfrey tea, similar to nettle tea below), beneficial insect attractor, mulch, weed suppressant (it can be used as a border around vegetable plots to stop the paths getting overrun with weeds, biomass accumulator, livestock forage, edible, a wound healer and it was traditionally called 'knit bone' by herbalists as it helps heals fractures and soft tissue injuries (owing principally to its allantoin content). It's an ideal permaculture plant.

Even though comfrey has long been esteemed as a vulnerary, it has come under scrutiny owing to its safety in recent years because of the discovery of the pyrrolizidine alkaloids. These are believed to be hepatoxic (toxic to the liver). Using comfrey externally as a poultice or as a compress has always been safe. However recent scientific studies indicate that comfrey, when ingested in large amounts and over long periods of time will cause liver damage. This is because of the pyrrolizidine alkaloids it contains. These pyrrolizidine alkaloids occur in a number of other plants as well, including ragwort, borage, and coltsfoot. In the 1980s there was a research paper that reported liver damage in laboratory animals that had varying doses of these alkaloids injected into them intravenously. This came as shock to the herbalist community because comfrey has long been regarded as one of the safest herbs. I make a comfrey root and lavender ointment, which I have successfully used to treat bruises, greenstick fractures, cartilage, tendon and ligament wrenches, and skin problems. It is also very good for deep tissue massage as it provides a viscous, healing medium which also contains beeswax and olive oil. Whilst the leaves can be used for a great tasting tea internally, the root is best used externally for safety reasons.

In the permaculture design, I have identified a marginal area which would benefit from comfrey cultivation (see above). The soil is damp, rich, and suitable for harvesting roots. Growing comfrey would eliminate other less useful plants owing to its vigour and the size of its leaves. The area is otherwise a 'neutral' space which would be hard to cultivate other plants owing to the low light intensity, and proximity of the greenhouse.

Comfrey has become an important plant for the organic gardening movement. It has thick, far reaching roots which access minerals deep in the soil, making it rich in potassium and nitrogen. The fast-growing leaves can be cut several times a year to make an organic slug control, liquid fertiliser, leaf mould and compost activator.