Comfrey

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For the place, see Comfrey, Minnesota.
Russian comfrey (Symphytum x uplandicum)

Comfrey (also comphrey) is a common name for plants in the genus Symphytum. Comfrey species are important herbs in organic gardening. It is used as a fertilizer and as an herbal medicine. The most commonly used species is Russian comfrey Symphytum × uplandicum ,[1] which is a cross or hybrid of Symphytum officinale (Common Comfrey) and Symphytum asperum (Rough Comfrey).

Description[edit]

Comfrey (Symphytum officinale L.) is a perennial herb of the family Boraginaceae with a black, turnip-like root and large, hairy broad leaves that bears small bell-shaped flowers of various colours, typically cream or purplish, which may be striped. It is native to Europe, growing in damp, grassy places, and is locally frequent throughout Ireland and Britain on river banks and ditches. More common is the hybrid between S. officinale and S. asperum, Symphytum × uplandicum, known as Russian Comfrey, which is widespread in the British Isles, and which interbreeds with S. officinale. Compared to S. officinale, S. × uplandicum is generally more bristly and has flowers which tend to be more blue or violet.[2]

Cultivation[edit]

Comfrey has long been recognized by both organic gardeners and herbalists for its great usefulness and versatility; of particular interest is the 'Bocking 14' cultivar of Russian Comfrey. This strain was developed during the 1950s by Lawrence D Hills, the founder of the Henry Doubleday Research Association (the organic gardening organisation itself named after the Quaker pioneer who first introduced Russian Comfrey into Britain in the nineteenth century) following trials at Bocking, near Braintree, the original home of the organization.[3]

The comfrey bed should be well prepared by weeding thoroughly, and dressing with manure if available. Offsets should be planted 0.6 - 1m (2–3 feet) apart with the growing points just below the surface, while root segments should be buried about 5 cm (2 inches) deep. Keep the bed well watered until the young plants are established. Comfrey should not be harvested in its first season as it needs to become established. Any flowering stems should be removed as these will weaken the plant in its first year.[4]

Comfrey is a fast-growing plant, producing huge amounts of leaf during the growing season, and hence is very nitrogen hungry. Although it will continue to grow no matter what, it will benefit from the addition of animal manure applied as a mulch, and can also be mulched with other nitrogen rich materials such as lawn clippings, and is one of the few plants that will tolerate the application of fresh urine diluted 50:50 with water, although this should not be regularly added as it may increase salt levels in the soil and have adverse effects on soil life such as worms. Mature comfrey plants can be harvested up to four or five times a year. They are ready for cutting when about 60 cm (2 feet) high, and, depending on seasonal conditions, this is usually in mid-Spring. Comfrey will rapidly regrow, and will be ready for further cutting about 5 weeks later. It is said that the best time to cut comfrey is shortly before flowering, for this is when it is at its most potent in terms of the nutrients that it offers. Comfrey can continue growing into mid-autumn, but it is not advisable to continue taking cuttings after early autumn in order to allow the plants to build up winter reserves. After the growing season, leaving comfrey beds fallow may deliver higher yields in future harvests, as the plant builds up energy reserves in its roots. [5]

Comfrey should be harvested by using either shears, a sickle, or a scythe to cut the plant about 2 inches above the ground, taking care handling it because the leaves and stems are covered in hairs that can irritate the skin. It is advisable to wear gloves when handling comfrey. Despite being sterile, Bocking 14 Russian Comfrey will steadily increase in size. It is therefore advisable to split it up every few years (and at the same time propagate more plants that can be shared with fellow gardeners!). It is however difficult to remove comfrey once established as it is very deep rooting, and any fragments left in the soil will regrow. Rotovation can be successful, but may take several seasons. The best way to eradicate comfrey is to very carefully dig it out, removing as much of the root as possible. This is best done in hot, dry summer weather, wherein the dry conditions will help to kill off any remaining root stumps. Comfrey is generally trouble free once established, although weaker or stressed plants can suffer from comfrey rust or mildew. Both are fungal diseases, although they rarely seriously reduce plant growth and thus do not generally require control. However infected plants should not be used for propagation purposes.[6]

Fertilizer uses[edit]

Comfrey is a particularly valuable source of fertility to the organic gardener. It is very deep rooted and acts as a dynamic accumulator,[7] mining a host of nutrients from the soil. These are then made available through its fast-growing leaves (up to 4-5 pounds per plant per cut) which, lacking fibres, quickly break down to a thick black liquid. There is also no risk of nitrogen robbery when comfrey is dug into the soil as the C:N ratio of the leaves is lower than that of well-rotted compost. Comfrey is an excellent source of potassium, an essential plant nutrient needed for flower, seed and fruit production. Its leaves contain 2-3 times more potassium than farmyard manure, mined from deep in the subsoil, tapping into reserves that would not normally be available to plants.[8]

There are various ways in which comfrey can be used as a fertilizer. These include:[9] [10]

  • Comfrey as a compost activator - include comfrey in the compost heap to add nitrogen and help to heat the heap. Comfrey should not be added in quantity as it will quickly break down into a dark sludgy liquid that needs to be balanced with more fibrous, carbon-rich material.
  • Comfrey liquid fertilizer - can be produced by either rotting leaves down in rainwater for 4–5 weeks to produce a ready-to-use 'comfrey tea', or by stacking dry leaves under a weight in a container with a hole in the base. When the leaves decompose a thick black comfrey concentrate is collected. This must be diluted at 15:1 before use.
  • Comfrey as a mulch or side dressing - a two-inch layer of comfrey leaves placed around a crop will slowly break down and release plant nutrients; it is especially useful for crops that need extra potassium, such as fruit bearers but also reported to do well for potatoes. Comfrey can be slightly wilted before application optionally but either way, avoid using flowering stems as these can root.
  • Comfrey as a companion plant for trees and other perennials. Soil tests confirm[11] that soil nutrients increase in the presence of comfrey even when it is not used as mulch, side dressing, or liquid fertilizer, but just allowed to grow.
  • Comfrey potting mixture - originally devised to utilize peat, now environmental awareness has led to a leaf mold-based alternative being adopted instead; two year old, well decayed leaf mold should be used, this will absorb the nutrient-rich liquid released by the decaying comfrey. In a black plastic sack alternate 7–10 cm (3-4 inch) layers of leaf mold and chopped comfrey leaves. Add a little dolomitic limestone to slightly raise pH. Leave for between 2–5 months depending on the season, checking that it does not dry out or become too wet. The mixture is ready when the comfrey leaves have rotted and are no longer visible. Use as a general potting compost, although it is too strong for seedlings.[12]

Propagation[edit]

Bocking 14 is sterile, and therefore will not set seed (one of its advantages over other cultivars as it will not spread out of control), thus is propagated from root cuttings. The gardener can produce his or her own ‘offsets’ from mature, strongly growing plants by driving a spade horizontally through the leaf clumps about 7 cm (3inches) below the soil surface. This removes the crown, which can then be split into pieces. The original plant will quickly recover, and each piece can be replanted with the growing points just below the soil surface, and will quickly grow into new plants. When choosing plants to divide, ensure that they are strong healthy specimens with no signs of rust or mildew. When dividing comfrey plants, take care not to spread root fragments around, or dispose of on the compost heap, as each can re-root, and comfrey can be a very difficult plant to get rid of. Offsets can also be purchased by mail order from specialist nurseries in order to initially build up a stock of plants.[13]

Medicinal uses[edit]

Contemporary herbalists have an ambivalent and controversial view of comfrey, despite a tradition of use by herbalists over history. Its traditional names of knitbone, boneset and the derivation of its Latin name Symphytum (from the Greek symphis, meaning growing together of bones, and phyton, a plant), speak to its long and widespread usage as a therapeutic herb.[14][15]

One of the most common modern-day uses of Comfrey extract is as a skin treatment. The plant contains the small organic molecule allantoin, which is thought to stimulate cell growth and repair while simultaneously depressing inflammation.[16] Some scientists and physicians agree that the use of Comfrey should be restricted to topical use, and should never be ingested, as it contains dangerous amounts of hepatotoxic pyrrolizidine alkaloids (PAs).[17][18] Studies associating comfrey with veno-occlusive disease (VOD), do not differentiate between Russian and common comfrey, plants with very different levels of PAs. VOD can in turn lead to liver failure, and comfrey has been implicated in at least one death, though type of comfrey being consumed, and other dietary, physiological and pharmacodynamic factors were not accounted for.[19] In 2001, the United States Food and Drug Administration issued a warning against internal usage of herbal products containing comfrey, and eventually banned Comfrey products intended for internal use.[20][21] In addition to restrictions on oral use, scientists and medical professionals recommend applying Comfrey extracts no longer than 10 days in a row, and no more than 4–6 weeks a year.[16][22]

One of the country names for comfrey was ‘knitbone’, a reminder of its traditional use in healing bone fractures. Modern science confirms that comfrey can influence the course of some types of muscle and joint pain.[23][24][25][26]

The allantoin contained in the plant is thought to help replace and thus repair cells in the body through its proliferant properties. Comfrey was used in an attempt to treat a wide variety of ailments ranging from bronchial problems, broken bones, sprains, arthritis, gastric and varicose ulcers, severe burns, acne and other skin conditions. It was reputed to have bone and teeth building properties in children, and have value in treating "many female disorders". Constituents of comfrey also include mucilage, steroidal saponins, tannins, pyrrolizidine alkaloids, inulin, and proteins.[27]

The flowers of Russian comfrey

Excessive doses of symphytine, one of the PAs in comfrey, may cause cancer in rats.[28] This was shown by injection of the pure alkaloid. The whole plant has also been shown to induce precancerous changes in rats.[29]

Most recently, in a placebo-controlled study comfrey was found to decrease back pain when used topically. However, it is not clear if these results reached statistical significance.[30]

References[edit]

  1. ^ Jacke, Dave & Toensmeier, Eric. Edible Forest Gardens. Chelsea Green, 2005, p. 490.
  2. ^ Stace, Clive (2010). New Flora of the British Isles (3rd ed.). Cambridge, UK: Cambridge University Press. ISBN 978-0-521-70772-5{{inconsistent citations}} , p. 557
  3. ^ N.A. "The history of Garden Organic". Garden Organic - the national charity for organic growing. Garden Organic. Retrieved 25 March 2014. 
  4. ^ N.A. "Comfrey". Oils and Plants. Retrieved 25 March 2014. 
  5. ^ Teynor, Putnam, Doll, Kelling, Oelke, Undersander, and Oplinger. "Comfrey". Alternative Field Crops Manual. University of Wisconsin, Extension, Cooperative-Extension. Retrieved 25 March 2014. 
  6. ^ N.A. "How To Grow Comfrey". The Garden of Eaden. Retrieved 25 March 2014. 
  7. ^ N.A. "How to Grow Comfrey". The Garden of Eaden. Retrieved 25 March 2014. 
  8. ^ permaculturebrittancy. "Everything you always wanted to know about COMFREY but were afraid to ask.". Not Dabbling In Normal. Not Dabbling In Normal. Retrieved 25 March 2014. 
  9. ^ Don, Monty. "Comfrey for compost: The superfood for plants". Mail Online. Daily Mail Online. Retrieved 25 March 2014. 
  10. ^ Nick, Jean. "Comfrey Power". Organic Gardening. Organic Gardening. Retrieved 25 March 2014. 
  11. ^ Stallings, Ben. "Does Comfrey Really Improve Soil?". Permaculture News. Permaculture Research Institute. Retrieved 27 June 2014. 
  12. ^ "Garden Benefits of Comfrey Powder Plants". Organic Gardening. Retrieved 2012-05-27. 
  13. ^ Teynor, T.M.; et al. (1997). "Comfrey". Purdue University. Retrieved 2012-03-16. 
  14. ^ Staiger, C (2013). "Comfrey root: from tradition to modern clinical trials". Wiener Medizinische Wochenschrift 163 (3–4): 58–64. doi:10.1007/s10354-012-0162-4. PMC 3580139. PMID 23224633. 
  15. ^ Yarnell, E (1999). "Misunderstood "Toxic" Herbs". Alternative & Complementary Therapies 5: 6–11. doi:10.1089/act.1999.5.6. 
  16. ^ a b "Comfrey: University of Maryland Medical Center". Retrieved 5 January 2012. 
  17. ^ Miskelly, FG; Goodyer, LI (1992). "Hepatic and pulmonary complications of herbal medicines". Postgrad Med J 68 (805): 935–936. doi:10.1136/pgmj.68.805.935. PMC 2399473. PMID 1494521. 
  18. ^ Miller, LG (1998). "Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions". Arch Intern Med 158 (20): 2200–2211. doi:10.1001/archinte.158.20.2200. PMID 9818800. 
  19. ^ Yeong M.L., et al.; Swinburn, Boyd; Kennedy, Mark; Nicholson, Gordon (1990). "Hepatic veno-occlusive disease associated with comfrey ingestion". Journal of Gastroenterology and Hepatology 5 (2): 211–214. doi:10.1111/j.1440-1746.1990.tb01827.x. PMID 2103401. 
  20. ^ "FDA/CFSAN - FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market". Retrieved 2007-06-01. 
  21. ^ Koll, R; Klingenburg, S (2002). "herapeutic characteristance and tolerance of topical comfrey preparations. Results of an observational study of patients". Fortschr Med Orig 120 (1): 1–9. PMID 14518351. 
  22. ^ Stickel, F; Seitz, HK (2000). "The efficacy and safety of comfrey". Public Health Nutr 3 (4(A)): 501–508. doi:10.1017/s1368980000000586. 
  23. ^ Kucera, M; Barna, M; Horàcek, O; Kàlal, J; Kucera, A; Hladìkova, M (2005). "Topical symphytum herb concentrate cream against myalgia: a randomized controlled double-blind clinical study". Advances in therapy 22 (6): 681–92. doi:10.1007/BF02849961. PMID 16510384. 
  24. ^ Kucera, M; Barna, M; Horácek, O; Kováriková, J; Kucera, A (2004). "Efficacy and safety of topically applied Symphytum herb extract cream in the treatment of ankle distortion: results of a randomized controlled clinical double blind study". Wiener medizinische Wochenschrift (1946) 154 (21–22): 498–507. doi:10.1007/s10354-004-0114-8. PMID 15638067. 
  25. ^ Koll, R; Klingenburg, S (2002). "Therapeutic characteristance and tolerance of topical comfrey preparations. Results of an observational study of patients". Fortschritte der Medizin. Originalien 120 (1): 1–9. PMID 14518351. 
  26. ^ Grube, B; Grünwald, J; Krug, L; Staiger, C (2007). "Efficacy of a comfrey root (Symphyti offic. Radix) extract ointment in the treatment of patients with painful osteoarthritis of the knee: results of a double-blind, randomised, bicenter, placebo-controlled trial". Phytomedicine : international journal of phytotherapy and phytopharmacology 14 (1): 2–10. doi:10.1016/j.phymed.2006.11.006. PMID 17169543. 
  27. ^ N.A. "Comfrey Leaf". Comfrey Leaf - Mountain Rose Herbs. Mountain Rose Herbs. Retrieved 25 March 2014. 
  28. ^ Rode, Dorena. "Summary of In Vivo Comfrey Studies". Retrieved 2008-02-20. 
  29. ^ Mei, N; Guo, L; Zhang, L; Shi, L; Sun, YA; Fung, C; Moland, CL; Dial, SL; Fuscoe, JC; Chen, Tao (2006). "Analysis of gene expression changes in relation to toxicity and tumorigenesis in the livers of Big Blue transgenic rats fed comfrey (Symphytum officinale)". BMC Bioinformatics. 7 Suppl 2: S16. doi:10.1186/1471-2105-7-S2-S16. PMC 1683566. PMID 17118137. 
  30. ^ Giannetti BM, Staiger C, Bulitta M, Predel HG (2009). "Efficacy and safety of a Comfrey root extract ointment in the treatment of acute upper or low back pain: results of a double-blind, randomised, placebo-controlled, multi-centre trial". Br J Sports Med. 44 (9): 637–41. doi:10.1136/bjsm.2009.058677. PMID 19460762. 

External links[edit]