Comfrey - a controversial Herb
Comfrey growing tall and fast.
The History, Culinary, Medicinal Uses and Cultivation of Comfrey, Symphytum officinale L.
by Maureen McCracken
Comfrey, Symphytum officinale L., is a perennial herb in the Boraginaceae family. It grows best in full sun, but will also do well in partial shade. Comfrey thrives in clay soil with plenty of moisture in zones 3-9; however, it is quite adaptable and tolerates a wide variety of conditions. Depending on the environment, Comfrey can reach heights of 3 to 5 feet tall on thick, hairy stems. Leaves are large and also hairy and differ in size and appearance depending upon stem position. Flowers appear in bell-like clusters in a color range from pink, purple, blue to white. The tap root is very long with a black exterior and white juicy interior. Because it is a very deep root, it is extremely difficult to eradicate once established. In addition, any root fragments remaining in the soil will take root and regrow. Therefore, it is best not to plant comfrey in cultivated areas as broken root bits will create many new plants. Comfrey also self-seeds. Between the self-seeding and root regrowth, comfrey can become invasive. There is a sterile species of comfrey, Symphytum x uplandicum ‘Bocking 14’, which eliminates the self-seeding problem in the garden.
Comfrey is a very fast growing plant. During the growing season it produces huge amounts of leaves. Mature comfrey plants can be harvested several times a year, as it will replenish itself very rapidly. Wear gloves when cutting comfrey as the hairy leaves and stems can irritate skin.
Fertilizer Uses of Comfrey. Comfrey is valuable to the organic gardener as a fertilizer source. Due to its deep root system, it is able to absorb significant amounts of minerals from the soil. Comfrey is an excellent source of nitrogen and potassium. The leaves contain 2-3 times more potassium than manure. Use comfrey leaves in your compost pile as an activator to heat the pile and to provide a source of nitrogen. The leaves of the comfrey plant can also be used to make a liquid fertilizer simply by placing leaves in water. Let the brew sit for approximately 5 weeks to produce a ready-to-use comfrey tea. You can also use leaves as nutritious mulch by placing a 2-inch layer of comfrey leaves in garden beds instead of regular mulch. When leaves break down nutrients are released into the soil.
Potential Dangers of Comfrey. Historically, comfrey has been used as a medicinal herb. One of its many common names is knitbone, relating to its historical use to aid in the healing of broken bones, bruises and sprains. It has also been used medicinally to heal wounds, gout, inflammation, ulcers, skin ailments and other illnesses. However, scientists have discovered comfrey contains a toxic substance known as pyrrolizidine alkaloids, a substance that can cause severe liver damage. Consequently in 2001, the FDA required that all oral comfrey supplements be removed from the marketplace. Canada, Australia, Germany and the UK have also banned the sale of oral products containing comfrey. Comfrey, growing in pastures, also poses a threat to livestock due to its damage to the liver. Horses, cows and pigs are most vulnerable to permanent liver damage and poisoning.
Use with caution, negative effects
Unfortunately, pyrrolizidine alkaloids are also absorbed through the skin. Therefore, even using a topical containing comfrey should be used very cautiously and only under the supervision of a knowledgeable health practitioner. Over time, harmful amounts of pyrrolizidine alkaloids may build up in the body. Any ointment containing comfrey should never be used on broken skin. The University of Maryland Medical Center recommends that only small amounts should be applied and for no longer than 10 days at a time, and not more than 6 weeks total per year. Comfrey should not be administered in any form to children, the elderly, pregnant or breast-feeding women.
Additionally, there is some concern that comfrey use may have other negative effects. The FDA notes that pyrrolizidine alkaloids may cause cancer. There is also concern that alkaloids in comfrey may cause kidney damage, lung damage, pulmonary edema and cirrhosis of the liver. MM July 2010
For further research on this controversial herb, the following Web site provides much information:
http://www.umm.edu/altmed/articles/comfrey-000234.htm
http://www.bccancer.bc.ca/PPI/UnconventionalTherapies/Comfrey.htm
http://www.drugs.com/npp/comfrey.html
by Maureen McCracken
Comfrey, Symphytum officinale L., is a perennial herb in the Boraginaceae family. It grows best in full sun, but will also do well in partial shade. Comfrey thrives in clay soil with plenty of moisture in zones 3-9; however, it is quite adaptable and tolerates a wide variety of conditions. Depending on the environment, Comfrey can reach heights of 3 to 5 feet tall on thick, hairy stems. Leaves are large and also hairy and differ in size and appearance depending upon stem position. Flowers appear in bell-like clusters in a color range from pink, purple, blue to white. The tap root is very long with a black exterior and white juicy interior. Because it is a very deep root, it is extremely difficult to eradicate once established. In addition, any root fragments remaining in the soil will take root and regrow. Therefore, it is best not to plant comfrey in cultivated areas as broken root bits will create many new plants. Comfrey also self-seeds. Between the self-seeding and root regrowth, comfrey can become invasive. There is a sterile species of comfrey, Symphytum x uplandicum ‘Bocking 14’, which eliminates the self-seeding problem in the garden.
Comfrey is a very fast growing plant. During the growing season it produces huge amounts of leaves. Mature comfrey plants can be harvested several times a year, as it will replenish itself very rapidly. Wear gloves when cutting comfrey as the hairy leaves and stems can irritate skin.
Fertilizer Uses of Comfrey. Comfrey is valuable to the organic gardener as a fertilizer source. Due to its deep root system, it is able to absorb significant amounts of minerals from the soil. Comfrey is an excellent source of nitrogen and potassium. The leaves contain 2-3 times more potassium than manure. Use comfrey leaves in your compost pile as an activator to heat the pile and to provide a source of nitrogen. The leaves of the comfrey plant can also be used to make a liquid fertilizer simply by placing leaves in water. Let the brew sit for approximately 5 weeks to produce a ready-to-use comfrey tea. You can also use leaves as nutritious mulch by placing a 2-inch layer of comfrey leaves in garden beds instead of regular mulch. When leaves break down nutrients are released into the soil.
Potential Dangers of Comfrey. Historically, comfrey has been used as a medicinal herb. One of its many common names is knitbone, relating to its historical use to aid in the healing of broken bones, bruises and sprains. It has also been used medicinally to heal wounds, gout, inflammation, ulcers, skin ailments and other illnesses. However, scientists have discovered comfrey contains a toxic substance known as pyrrolizidine alkaloids, a substance that can cause severe liver damage. Consequently in 2001, the FDA required that all oral comfrey supplements be removed from the marketplace. Canada, Australia, Germany and the UK have also banned the sale of oral products containing comfrey. Comfrey, growing in pastures, also poses a threat to livestock due to its damage to the liver. Horses, cows and pigs are most vulnerable to permanent liver damage and poisoning.
Use with caution, negative effects
Unfortunately, pyrrolizidine alkaloids are also absorbed through the skin. Therefore, even using a topical containing comfrey should be used very cautiously and only under the supervision of a knowledgeable health practitioner. Over time, harmful amounts of pyrrolizidine alkaloids may build up in the body. Any ointment containing comfrey should never be used on broken skin. The University of Maryland Medical Center recommends that only small amounts should be applied and for no longer than 10 days at a time, and not more than 6 weeks total per year. Comfrey should not be administered in any form to children, the elderly, pregnant or breast-feeding women.
Additionally, there is some concern that comfrey use may have other negative effects. The FDA notes that pyrrolizidine alkaloids may cause cancer. There is also concern that alkaloids in comfrey may cause kidney damage, lung damage, pulmonary edema and cirrhosis of the liver. MM July 2010
For further research on this controversial herb, the following Web site provides much information:
http://www.umm.edu/altmed/articles/comfrey-000234.htm
http://www.bccancer.bc.ca/PPI/UnconventionalTherapies/Comfrey.htm
http://www.drugs.com/npp/comfrey.html
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Maureen McCracken is an Extension Master Gardener Volunteer for Mecklenburg County, NC.
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