by Richard Alan Miller, c1993

The Controversy:

The future of comfrey is uncertain now, especially with new rulings in both Canada and the U.S. on its limited use as a food. However, many of these political stands are built on sand and may soon be challenged in the courts. Long touted as one of the most popular herbs in European folk medicine, comfrey has become increasingly controversial because of reports that it is toxic to the liver, and perhaps carcinogenic.

At issue is a class of chemicals called pyrrolizidine alkaloids (PAs). Alkaloids of this type are responsible for the toxicity of such poisonous plants as Helliotropium, Crotalaria, and Senecio. They have caused substantial losses of grazing livestock, and some human poisonings as well. The alkaloids damage the veins within the liver, causing a condition known as hepatic veno-occulsive disease (HVOD). Different PAs have different toxicity, further complicating matters.

Comfrey has been known since at least the 1960s to contain PAs, which in sufficient doses, have caused liver damage and tumors in lab animals. The risk to humans is a matter of serious debate, while international government regulation is showing a trend toward eliminating the causal consumption of comfrey. Comfrey root is much higher in alkaloids than leaf, and younger leaves contain more than older leaves. For perspective, spinach and chard also contain similar quantities of these PAs.

The U.S. FDA has sampled a variety of comfrey products for analysis, and will ultimately make a decision about how such products are to be regulated. Australia has banned comfrey, while Canada has proposed a ban on its use in food and restricted its medicinal use. Germany and New Zealand have also restricted its use.

The first Canadian action was taken in 1982, when the Health Protection Branch of Health and Welfare Canada introduced an amendment to Canada's Food and Drug Regulations which prohibits the sale, for medicinal purposed, of any products containing echimidine (Canada Gazette, 30 March, 1988). Echimidine, considered to be the most toxic of comfrey PAs is not found in common comfrey (Symphytum officinale L.)

However, it is present in prickly comfrey (S. asperum Lepchin) and its hybrids with S. officinale L., including Russian comfrey (S. x uplandicum Nyman), which is the most commonly encountered commercial comfrey. Examination of comfrey products reveal that none are ever designated or labeled as Russian comfrey or by its Latin binomial. Products continue to be labeled as either simply "comfrey" or Symphytum officinale (common comfrey).

New Canadian legislation is now designed to have more careful attention paid to identification of botanical species by the herbal industry. In my review, there is still no intent to underestimate the relative potential danger of echimidine-free S. officinale. While S. officinale has been shown to be carcinogenic in rats, the methodology and dose rates were so high as to be make results suspect. Without this labelling, however, the "baby might get thrown out with the bathwater."

There are numerous studies now available that show the benefits of using comfrey leaf (S. officinale) as an animal food supplement. This is especially true for older plants, where the leaf is taken prior to the "10-percent" flowering stage, much like alfalfa. While the root is quite high in PAs, there are absolutely no PAs shown to exist when 3-year-old comfrey leaf is cut at this stage of growth.

All reported toxic reactions in humans (only 4!) are from individuals who took massive doses of leaf , either by juicing it, or large quantities of tablets. However, when used as a 50-percent supplement to cattle, not only are there no reported toxic reactions, apparently it is metabolized into harmless proteins, including two essential amino acids missing in alfalfa (lysine and alanine). When combined with alfalfa, this mixture becomes a "whole food" for the cow! Allantoin is also considered very important to cattle, especially those in feed lots where chance of disease and infection is so much higher.

While debate continues on the safety of comfrey, current evidence indicates that commercial comfrey preparations are not always derived from S. officinale. Uncertainties in the marketplace are compounded by errors in the scientific literature, further complicating safety evaluation. The presence of echimidine (likely the most toxic alkaloid) in commercial products has led the Canadian government to propose a general ban on comfrey. In the U.S. the American Herbal Products Association and the FDA are both reviewing the literature on comfrey to determine what action may be appropriate regarding marketing of comfrey products.

History Of Usage:

Since comfrey contains almost 35 percent protein, vitamin B12, and cell-proliferent allantoin, attempts have been made to extract it for human consumption. Comfrey is, however, an important animal feed supplement in some parts of the world. It is also grown as an organic compost and mulch.

Both leaves and roots have been used medicinally. The plant roots have the largest content of mucilage, allantoin, symphytine, echimidine, isobauerenol, beta-sitoosterol, tannins, and lasiocarpine. It is for this reason that comfrey root has not historically been used for internal consumption. The tannins are responsible for the astringent properties of the plant parts, and the allantoin mucilage accounts for a demulcent activity.

Comfrey leaves are used as an external remedy as a poultice with thoroughbred race horses with shin splints and bone spur problems. In dehydrated and pellet forms it make a useful cattle fodder. Comfrey root is a demulcent used in cough mixtures in the form of a decoction. It has also been used as an ingredient combined with dandelion and chicory root for use in a non-caffeinated herbal "coffee" substitute. Comfrey is also use in cosmetic products, such as Nexus Hair Conditioner.

Field Production:

Comfrey is cultivated from rootstock. Roots from an older field are quartered and cut into 3 to 5 inch lengths by hand. They are planted 1.5 to 2 inches deep and one foot apart in rows (some recommend) planting 4 inches deep, but this can lead to rotting before emergence. Use 17 to 20 inch furrows, depending on available cultivation equipment parameters. Some 6 to 10 inches of rootstock can be taken from an established field every fourth year with one acre reseeding five acres.

Comfrey likes nitrogen, encouraging the lush leaf growth. Manure adds too many weeds. The taproot can grow to six feet within three years. Comfrey thrives in heavy irrigation while it sets up its root system the first year. Use up to a five-day rotation on well-drained soils. Weed control is done by cultivation until the field begins to mature somewhat. This forms an "umbrella effect" and markedly discourages weed growth. The broad leaves compete successfully with many weeds.

When starting a new field, grasses are the primary problem when first establishing the field. Just at first emergence from the split rootstock, a light application of RoundUp will kill the full grasses and only "burn" the comfrey back one week. RoundUp is one of the few herbicides that truly breaks down into minerals and salts within 10 days of application. As a "translocator," it's primary action is to prevent photosynthesis, not a problem at this stage of growth for comfrey.

If you choose not to use RoundUp, cultivation should be handled via listers. First and second cuttings are usually not marketable because of grass contamination. Once the field "sets," the so-called "umbrella effect" takes over and grasses are more easily confirmed or eliminated. This method, while being strictly by the rules of "organic" farming losses one year in production. If RoundUp is necessary, no further applications are ever necessary.

Harvesting Technique:

Comfrey leaf should be cut before 10 percent of the crop goes to flower. It cannot be dried in the sun because of the high mucilage. Even comfrey from an alfalfa dehydration pellet mill will rot from the center. The best form of harvest is to cut comfrey leaf at 6 inches from the ground with a side-bar cutter, attempting not to bruise the leaf as this darkens the final color of the dried leaf.

The comfrey is laid out in wide windrows, avoiding leaf stacking and compaction. Let the leaf come to a 50 percent sun-cure, and then pick it up using a draper or other type conveyor-type delivery to wagons. Some can use a flail-chop if the end use is for cattle. While this may darken the leaf, cattle are less concerned with appearances.

The wagons should be taken to large dehydration facilities for final drying. These facilities can be hop kilns, tobacco dryers, and plywood kilns. Grain dryers are too small. Basically, forced warm air shafts work best. This gently concluded the final drying of the leaf. Comfrey is easy to grow, but the key to success with this crop lies in proper dehydration.

The plant design needs to consider the shear volumes involved. Most fields in third year production will experience a minimum of six cuttings. Each cutting will have more than 10,000 pounds of wet produce per acre. One 30-foot by 30-foot kiln floor will hold up to two acres per 8-hour period of air drying. How do you propose to load and unload this product from wagons into a kiln, and how do you unload a kiln - especially if you are farming 20 acres? This will need some thought, and is the "proprietary" aspects of successful comfrey ventures.

Once the comfrey leaf is dried, it is usually put into 180-pound rectangular bales, wrapped in burlap (much like hops). Since it is quite light, the "cube" is bulky, so dimension of the bale are designed for stacking in a warehouse. If the product is to be used for animal feed supplements, then a simple pellet can be used, with 50-pound sacks (like dehydrated alfalfa).

Root harvests can be done with potato digging equipment. If they are to be taken for replanting a field, care must be taken to pile and cover the roots with tarps. Exposure to sun will often dry the root to a point that it will be hard or slow to begin re growth. Sunlight triggers the root into stasis. Sun-cured roots for the cosmetic industry are packed in either burlap or fiber drums.

The powder of comfrey leaf is green, almost odorless, and has a mucilaginous, weakly astringent taste. Product should be of more or less uniform color with little or not "browning" evident. As the flowers are edible, their inclusion is fine, except where high product uniformity is necessary.

Underground comfrey root is spindle shaped, branched, often more than 2.5 inches thick and more than 5 feet deep. It shows external wrinkles, has a firm, horny texture, and dark color./ The inside ranges from creamy white to a dark brown color. The root is almost odorless, and has a sweetish, mucilaginous, feebly astringent taste.

Powdered comfrey root is grayish brown in color with a many small dark brown specks of outer bark on it. It contains a mucilage which is water soluble. It should not be taken internally, as previously discussed.


Comfrey is traditionally sold to processors (for milling) and manufactures. Prices vary, depending on availability and volume of sale. Most current sales to small processors is usually in 2 to 4-ton lots. A typical mid-sized wholesaler will use up to 20 ton, depending on statewide FDA recommended compliance. This is changing, and less and less comfrey is sold for retail distribution. Most comfrey now goes to manufactured cosmetics and topical applications.

The price for comfrey leaf has increase to about $1.50 per pound in 2-ton quantities. Comfrey root can fetch up to $2.80 per pound, again depending on availability. These two markets are limited, and becoming more so because of concerns about PAs and other potential and "unknown" carcinogenic.

There is, however, another very large and potentially important new market as an animal food supplement. Recent studies with comfrey leaf have shown that it contains several essen­tial amino acids missing in alfalfa. When it is combined with alfalfa in a 60/40% ratio, it constitutes a "whole food" for feedlot cattle. The poten­tial future markets for this crop in combination with other currently pro­duced feeds can become very significant, with availability.

With a pellet-combination price of $400/ton, the demand within five years for a new animal feed could be more than 50,000 acres. This would represent more than 300K ton. Mixed with birdseed, the exotic bird (ostrich) markets are growing more than 500%/year, while the racetrack industry cannot get enough of these specialty feed mixes.


Crop: Comfrey Leaf (Symphytum officinale L.)

Advantage: Potential animal food additive.

Major Use: Major food additive, cosmetic, pharmaceutical use.

Climate Requirements: 5.3-8.7 pH, 19.7-106.2 inches annual precipitation, 42.8-77.2 degrees F.

Nature Of Product: Sold as herb, extract and root. New market as animal feed pellet.

World & Domestic Volumes: Unknown. Estimate world use as F/D at 8,000 ton. Domestic F/D is 800 ton.

Current Sources of Supply: South America, Germany, Yugoslavia, Russia.

Domestic Production Potentials: 1,000 ton/month/state as cattle food, or 600,000 dry weight tons by 1996.

Competition: Oregon, California, Brazil, Germany, Yugoslavia.

Equipment Needs To:

Grow: Irrigation, row crop, cultivation, rotary mower or draper (conveyor pickup)

Process: Large dehydration system, pellet mill, bagging.

Store: Poly bags, pallet load, heated storage.

Market: Samples, broker.

Cultural Problems: Grass control during first two years.

Marketing Problems: Federal regulations, FDA concerns, new market for animal feeds.



Purpose - To determine the suitability of cultivating comfrey leaf on the Grants Pass Mint Farm as an alternative cash crop. To determine the cultivation, harvest and drying problems associated with comfrey leaf.

Objective - To develop accurate cost-of-goods produced for culti­vating, harvesting and drying this crop for expansion considerations. To solve specific technical problems already outlined. To begin developing animal food markets for this crop and show profits.

Scope - This should be developed as a multi-phased program. Phase I would be to plant a 10-acre field study for cultivation costs and soil amendment requirements. Begin a search for dehydration options, including the 7 hop kilns at Sunnybrook Hop Farm (Grants Pass). These dehydrators can be used for other crops.

Time Frame - The planting should occur in the early spring of 1990, with full commitment to begin research at that time. Rootstock avail­ability may limit the size of the study. First harvests will become avail­able in one year (Spring, 1991), unless a field already established can be located.

Anticipated Costs - Rootstock will cost about $600/acre, plus la­bor to prepare and plant the field. Access to the local hop kilns should be no problem since they are no longer used for hop production. Consultant fees (Richard Alan Miller) should include travel. Estimate Phase I to be less than $20,000 in total costs.

Anticipated Incomes - In full production, comfrey leaf yields should be in excess of 6 ton/acre (dry-weight), with 5 to 6 cuttings. Pre­vious studies in this area indicate that costs should be less than $320/ton, showing a minimum gross profit margin in excess of $800/acre. With addi­tional processing, profit margins can be increased significantly with pro­duction and market diversification.

Anticipated Volumes - Estimate more than 10 ton semi-green (30% sun-cure/wilted) product for dehydration per acre with each cutting. Dry-weight yields are estimated to be more than 1.2 ton/acre/cutting, with up to 6 cutting per year in this region.

Potential Markets - The current domestic tea markets for comfrey leaf are more than 400 ton, with world markets greater than 4,000 ton. The potential for a new animal feed made from comfrey leaf and other standard hay-type crops (alfalfa or birdseed) is astronomical. Now estimate this market to be in excess of 4,000 ton/month just for the cattle food markets of Japan alone.


Recent studies with comfrey leaf have shown that it contains several essen­tial amino acids missing in alfalfa. When it is combined with alfalfa in a 60/40% ratio, it constitutes a "whole food" for feedlot cattle. The poten­tial future markets for this crop in combination with other currently pro­duced feeds can become very significant, with availability.

With a pellet-combination price of $400/ton, the demand within five years for a new animal feed could be more than 50,000 acres. This would represent more than 300K ton. Mixed with birdseed, the exotic bird (ostrich) markets are growing more than 500%/year, while the racetrack industry cannot get enough of these specialty feed mixes.

Richard Alan Miller has assisted in the production of this crop with five different agri-businesses and numerous smaller producers for more than ten years. He has even sold some comfrey pellets and cubes to Japanese markets in Osaka. He feels that the Grants Pass Mint Farm could be best used for alternative cash crops, like comfrey.

Richard Alan Miller is available as an outside consultant to put together this and other related cash crops. His primary expertise lies in marketing and processing (adding value.)



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In addition, you can visit Richard Alan Miller's home page for a listing of his writings, also containing links to related subjects, and direction in the keywords Metaphysics, Occult, Magick, Parapsychology, Alternative Agriculture, Herb and Spice Farming, Foraging and Wildcrafting, and related Cottage Industries. Richard Alan Miller is available for lectures and as an Outside Consultant. No part of this material, including but not limited to, manuscripts, books, library data, and/or layout of electronic media, icons, et al, may be reproduced or transmitted in any form, by any means (photocopying, recording, or otherwise), without the prior written permission of Richard Alan Miller, the Publisher (and Author).


Uploaded: 12-23-05