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Comfrey, also known as knitbone, boneset, or common comfrey, is a perennial herb with turnip-like roots, and hairy, broad leaves. The plant bears bell-shaped flowers, from white to pink or purple in color. It is commonly used for medicinal purposes, but is also popular in organic gardening for its use as a fertilizer.
Native to Europe, comfrey prefers to grow in damp and grassy areas. It is widely found in the British Isles, growing along ditches and riverbanks. It is fast growing and produces large amount of foliage during the spring and summer. Mature plants can be harvested up to five times per year.
In herbal medicine, comfrey is known as an herb that can offer therapeutic benefits, but at the risk of liver toxicity. Taking any part of the plant internally may cause liver damage. In 2001, the United States Food and Drug Administration (FDA) issued a warning against its internal use. It should only be consumed under a doctor’s supervision for short periods of time. The herb is considered completely safe for external applications such as poultices or ointments.
Traditionally, comfrey has been used to treat broken bones, sprains, arthritis, ulcers, burns, acne, and female reproductive problems. Medical science has proved that the herb has an effect on healing bones. This confirms the use of one of comfrey’s popular folk names, boneset. Common home remedies include ointments for external sores, teas and infusions for lung and bone ailments, and poultices for sprains, sores, burns or blisters.
Comfrey is an astringent, anti-inflammatory, and hemostat. It aids in cell growth and absorbs toxins from the intestines, regulating intestinal flora. The plant contains antioxidant vitamins C, A, and E, and sodium, potassium, manganese, magnesium, protein, phosphorus, and B vitamins. Allantoin, tannins, saponins, and beneficial alkaloids can also be found in comfrey.
In organic gardening, comfrey’s beneficial use as a fertilizer is due to its deep root system. The plant is known as a dynamic accumulator, or a plant that mines nutrients from the soil through its roots. These nutrients are then made available in the large, broad leaves. They can be given back to the soil by using the plant itself as a fertilizer, or as part of a fertilizer mixture.
Comfrey is an excellent source of potassium, which is necessary for the production of flowers, seeds and fruits. The leaves of the comfrey plant include up to three times more potassium than manure. Its deep roots are able to tap into the subsoil, which is out of reach of most other plants.
In many English gardens, comfrey is so common you can't give it away. That's helpful, though, since it makes such good fertilizer. My parents are gardeners and really enjoy using it in the garden.
I've been told that it can irritate your skin if you have any minor cuts, though, so it's a good idea to wear gloves when working with it.