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Symphytum peregrinum Ledeb.

Boraginaceae
Comfrey, Russian comfrey, Quaker comfrey

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

Comfrey, mainly cultivated as green forage, can be used with maize to make ensilage. Comfrey is difficult to conserve because of the low amounts of carbohydrates. It is also used as a green vegetable, some cooking it in two waters and serving it with chives. Only small and medium leaves are used. They may be boiled or steamed for 2 minutes, and then eaten in salads or with a sauce. Comfrey is an ingredient in various herbal, pharmaceutical, and cosmetic preparations such as creams, eyedrops, hair products, lotions, and ointments (Leung, 1980). It is said to be antiinflammatory. The mucilage is thought to soften the skin when used in baths. Some organic gardeners recommend a mixture of comfrey and kudzu leaves for composting.

Folk Medicine

Plant contains allantoin, used in some face creams, or to cure scours in pigs and calves, or give a bloom to horses. For humans, it is reported to be good for asthma, whooping cough, stomach and duodenal ulcers and lung ailments. Gerard's herbal is quoted in the New Scientist (July 15, 1976, p. 14.) on multicolored Comfrey, variously known as Abraham, Isaac and Jacob, Pigweed, Suckers or Church Bells. "The slimie substance of the roote made in a posset of ale and given to drink against the pain in the backe gotten by any violent motion such as wrastling or overmuch use of women, doth in foure or five days perfectly cure the same, although involuntarie flowing of seed in men be gotten thereby." Comfrey is said to be alterative, astringent, demulcent, emollient, expectorant, hemostat, nutritive, and vulnerary. The root decoction is used as a mouthwash or gargle for asthma, bleeding gums, hoarseness, sore throat and stomatitis. It is also used for arthritis, bronchitis, bloody urine, cough, dysentery, dysmenorrhea, enterorrhagia, gallstones, gastritis, hematochezia, hematuria, hemoptysis, internal ulcers, leucorrhea, metrorrhagia, scrofula, tonsilitis, and ulcers of the kidney. In a vague reference Hutchens (1973) quotes S. Clymer (1963) "Numerous uncontradicted reports of lung cancer cured where all other means have failed and in which the sole treatment consisted of infusion made from the whole green plant and, even in some instances, of infusion made from the powder of the entire plant." Interestingly, comfrey does contain b-sitosterol which shows anticancer activity against the Lewis Lung Carcinoma Adenocarcinoma 755 and Walker Carcinosarcoma 256 tumor systems. Homeopathically, comfrey is prescribed for abscess, bone cancer, breast, enlarged glands, eye pain, fracture, gunshot wounds, hernia, menstrual arrest, sexual abscess, sprains and wounds (Hutchens, 1973). Allantoin, present in comfrey leaves and roots is said to be a cell proliferant, making the edges of wounds grow together and healing sores.

Chemistry

Per 100 g, comfrey is said to contain 0.5 mg thiamine, 1.0 mg riboflavin, 5.0 nicotinic acid, 4.2 mg pantothenic acid, 0.07 mg Vit. B12 (rare in vegetarian diet), 28,000 IU Vit. A, 100 mg Vit. C, 30 mg Vit. E and 0.18 mg allantoin. So-called Russian comfrey (84.93% water) contains (ZMB) 22.73% CP, 5.39% EE, 4.22% NFE, 21.25% ash, 5.35% silica, 2.02% Ca, and 0.57% P. Based on 16 analyses, prickly comfrey (83.1 to 89.8% H2O) contained (ZMB): 16–23% protein, 1.0–2.8% EE, 11.9–18.2% CF, 12.4–22.1% ash, and 43.2–49.1% NFE. The root contains 0.75 to 2.55% allantoin and about 0.3% alkaloids (symphytine, echimidine), lithospermic acid (said to be antigonadotrophic), 29% mucopolysaccharide (of glucose and fructose). There is a gum consisting of L(-)-xylose, L-rhamnose, L-arabinose, D-mannose, and D-glucuronic acid. Also reported are 2.4% pyrocatechol tannins, 0.65% carotene, glycosides, isobauerenol, b-sitosterol, stigmasterol, steroidal saponins, triterpenoids, (e.g. isobanerenol), choline, consolidine, silicic acid, lasiocarpine, viridiflorine, echinatine, and heliosupine-N-oxide (List and Horhammer, 1969–1979). According to Morton (1975), "Comfrey (Symphytum officinale L.) has considerable tannin in the leaves and the infusion of the dried leaves is very astringent. Comfrey root possesses 2.4% tannin...used in Germany for tanning leather. The above-ground plant contains the alkaloid lasiocarpine...consolidine and the N-oxide of heliosupine. Additional alkaloids have been found in the root... The acid fraction of an aqueous extract of the plant has shown antigonadotrophic activity in mice." According to Cancer Treatment Reports (1976; p. 1176), tannin-containing extracts from several plants produced either sarcomas or liver tumors. Tannic acid is hepatotoxic and several workers report that tannic acid or tannin extracts from plants were oncogenic in animals. On p. 1183, lasiocarpine is reported as an oncogenic compound. Based on these Cancer Treatment Reports, one might conclude that comfrey contains two oncogenic or tumor-inducing substances.

Description

Perennial, shrubby herb, with powerful mucilaginous roots that go down to a depth of 2–2.5 m; basal leaves lush, forming a rosette the first year, 30–100 cm long; stem-leaves hairy, petioled, broad pointed, often up to 5 cm in length, rough-textured, on succulent, grooved stems; inflorescence tall, terminal cyme, up to 1.3 m tall (to 3 m tall on good rich soils); flowers magenta-pink, or blue, bell-shaped; plant usually does not set seed.

Germplasm

Several vegetable strains of comfrey are known, the best cvs being 'Webster Strain' and 'Backing No. 14'. Some horticulture cvs are yellow-variegated or with yellow-margined leaves. (2n = 36)

Distribution

Native to the Caucasus, Russia and Persia, where it grows up to 1350 m elevation. Introduced and cultivated in England, United States, Canada (British Columbia), Kenya, North Rhodesia, New Zealand, Australia.

Ecology

Comfrey is suitable for the temperate and subtropical regions. It will grow and produce where many other forage plants will not. Almost any soil that allows deep root penetration (to about 2.5 m) will grow comfrey. The crop needs lots of water, and will stand flooding. Manures and fertilizers, particularly potash, should be added to the soil. Comfrey will grow in partial shade. The above-ground foliage will stand 15° of frost for a short time, and the roots will stand winter temperatures of -40°C. In the Crop Diversification Matrix, comfrey is reported to range from the Boreal Moist Forest Life Zone to the Warm Temperate Moist Forest Life Zone, tolerating annual biotemperature of 6–15°C, annual precipitation of 5–11 dm, and pH of 5.3–6.8.

Cultivation

Propagation is mainly by divisions of the crown or root cuttings, started in nursery beds. Comfrey usually does not produce seed, and plants obtained from seed are very often inferior. Rooted divisions are planted out in the spring (or in the autumn) as soon as frost does not endanger the foliage. They should be planted in rows 1 m each way. The crop should be kept weed free until the plants are established. After that there is no weed problem. Both mechanical and manual techniques may be used. Irrigation may be necessary, as the plant requires a lot of water. Fertilization of the soil is necessary to keep the fields producing well, the fertilizer being best applied at end of April or beginning of May, at rate of 400 kg/ha of a 5-20-20 formula. Soil should be adjusted to pH 6.5.

Harvesting

Plants last about 20 years or so. However, the plants should not be allowed to flower as they produce less, the amount of protein in the leaves is reduced and the amount of fiber increased. The leaves should be cut about 5 cm above the ground, the height adjusted so that neither the crown nor young shoots be injured. A first cutting can be made some months after planting when the plants have a good growth. A mowing machine is used. Three or four cuttings per year are possible with well established healthy plants.

Yields and Economics

Comfrey has a reported potential of 247 MT/ha of green fodder, but the average is usually less than that figure, about 237 MT/ha reported from England. Australia claims up to 250 MT/ha green fodder, with 33% protein based on dry material. Such biomass would have the energetic equivalent of 30 to 40 barrels of oil per hectare. According to U.S. Oil Week (Sept. 17, 1979), an Oregon company, Western Comfrey refines the plant into a 25% protein cattle feed selling for $210 a ton. It is estimated to produce 2–2.5 gal alcohol/bushel with 44% protein cattle feed as a byproduct. Agri-Fuels of Portland put up $1.5 million to build a distillery to turn out 1 million gallons fuel grade alcohol along with tons of rich cattle feed.

Energy

Figures available suggest that DM Yields would be in the range of 10 to 25 MT/ha/yr and that poor land, such as the types now commonly employed for rough-grazing, could be used. The ratio of output to input energy for native perennials is estimated at 4–10 times higher than in arable crops (Palz and Chartier, 1980). Actual yields will vary considerably with conditions; soil depth may prove to be an important parameter. In the absence of definitive yield information, an average yield of 17.5 MT DM/ha/yr is assumed. In the absence of experimental energy determinations, a conservative figure of 17.5 GJ/MT is also assumed. The cost of establishing the energy farm is based on a published figure for comfrey (cost of initial establishment, spread over 10 years, with interest on the outstanding balance at 12% = $461/ha/yr), but may be considerably less for vigorously spreading species such as Polygonum, Pteridium, and Urtica. The likely cost is ca $2.00 to $2.50 per GJ. If the initial planting cost could be halved, it would cost only $1.40 to $1.80 per GJ, at which level these energy sources would be competitive. As feedstock to anaerobic digestion, perennial crops at $2.25/GJ gross thermal value would give a feedstock cost of $3.75/GJ of product gas (without transport and storage) and a probable minimum gas cost of $8.25 per GJ. These figures are based also on harvesting cost of $75.00/ha (Palz and Chartier, 1980).

Biotic Factors

Grasshoppers, slugs, cutworms and pyrethrum eelworms have been reported as the worst pests. Several nematodes also attack comfrey: Meloidogyne hapla, M. javanica and several species in East Africa. The following fungi have been found on comfrey: Corticium solani, Pleospora herbarum, Stemphylium botryosum (leaf spot) and Sclerotium rolfsii.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw