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Sunday, February 15, 2009

Species of the Month: Comfrey

Species of the Month: Comfrey
by Douglas Barnes

Updated: Correction made.

Comfrey (Symphytum officinale). What better plant to feature as Species of the Month than this herbaceous member of the Boraginaceae family?

It grows up to 150 cm tall and 60 cm in diameter in warm climates. The optimum growth is in climates where day and night are equal (i.e. the tropics). There, production of 100 to 200 tons per acre (roughly 250 to 500 metric tons per hectare) is possible! However, it will grow in temperate regions. It prefers full sun and soils rich in nitrogen and humus, so interplanting with nitrogen fixers and mulching is a good idea. You can expect to get at least 10 years out of one plant, and a well-attended plant might outlive you!

Animal Fodder

It is protein rich with 15 to 30% dry-weight protein content, rivalling some legumes. It is used as a pig fodder successfully in amounts up to 80 to 90% of the diet! For poultry, it can reduce the need for other feed (be that your concoction or processed feed) by 50%. Egg quality will improve with yolks being brighter. Cows don’t bloat when eating comfrey like they do with clover. And too much clover can taint the milk – not a problem with comfrey. Also, mastitis is reduced in cows fed comfrey. Wilted comfrey mixed with straw fed to sheep at a ratio of one part comfrey to one and a half parts straw increases the digestion of the straw. The flowers make it useful as bee fodder. It is used in zoos as fodder for many (expensive) animals. Its tremendous production rates make it a great elephant feed.

Soil Improvement

Comfrey has deep roots that help it to draw up nutrients from subsoils. This characteristic makes it a valuable nutrient cycler. It accumulates nitrogen, potassium, phosphorus, calcium, zinc, manganese, magnesium, copper, sodium, sulfur, chromium, molybdenum and lead (the latter might make it useful in cleaning roadside soils contaminated by the use of leaded gasoline). It can be used as a green manure, and its ability to be cut right down to the ground a few times a year helps in this respect. It can be used as a compost activator.

It can be made into a liquid plant feed:
Place harvested comfrey in a sealable bucket
Weigh down the comfrey with a stone
Wait 1 or 2 weeks
Drain out the juice and dilute it 10 to 1 with water and water your plants with it
You can also use it to fill niches to suppress weeds.

As Food

Traditionally the whole plant has been used. Young leaves can be added to salads in small quantities to boost nutrient uptake. The stems can be blanched and eaten like asparagus. It is the only known plant source of vitamin B12.

As Medicine

Contains allantoin, which assists in the repair of damaged tissues. It is used as a poultice for cuts, scrapes, burns, skin conditions, ulcers, broken bones, strains and aches. It can help with digestive problems. The juice from leaves can be rubbed into the coats of dogs with mange.

The full catalogue of uses is:
Vulnerary (wound healer)
Astringent (contracts tissue making it useful to treat bleeding, peptic ulcers, diarrhoea, shrink mucus membranes, etc.)
Expectorant (dissolves mucus making it useful in treating phlegm)
Emollient (smoothes and softens skin)
Demulcent (treats inflamed, irritated tissue by coating it – e.g. treating a dry cough)
Antiseptic (helps treat or prevent infection in wounds)
Nutritive (along with its protein and minerals, it contains vitamin B1, B2, B3, B5, B6, B12, C, E and 28,000 IU of vitamin A per 100g)
Styptic (helps stop bleeding)
Antioxidant (from the rosmarinic acid it contains)
Pest Control

Slugs go for comfrey, so you could use it to attract slugs away from plants. If you really want to go all out against slugs, grow a ring of comfrey around your garden, separating the garden with an electric fence. The comfrey will attract the slugs from the garden. Then run pigs in the comfrey. The pigs will love both the comfrey and the slugs. And the pig urine and manure will attract in even more slugs, hopefully depleting your local population for a while. In place of the pigs, poultry could be run as well.

Caution Needed?

Comfrey does contain pyrrolizidine alkaloids which have the potential for liver damage. There have been warnings put out against the use of the herb, but evidence of incontrovertible documented toxicity is lacking. In the book “The Safety of Comfrey,” J.A. Pembery found no reported cases of pyrrolizidine poisoning from comfrey. He did find one case of pigs in Germany being poisoned by nitrates in comfrey, but not by pyrrolizidine. Lab tests on rats suggest that to cause harm to humans, one would have to eat about 20,000 leaves. Certainly from anecdotal evidence, many people have eaten comfrey without reservations for decades and been very healthy. Still, to err on the side of caution, limit consumption. Also, drying the comfrey reduces the amounts of alkaloids.

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seanpforde said...

Hey - great post, great blog. I think your pictures are really helpful for visualizing the relationships. Keep up the contributions!

DJEB said...

Sean, I'm glad you like the site. More is on the way!

Anonymous said...

Hi...i've heard great things about this plant...and the brilliant properties it holds...but i've been told by alot of people that you cannot ingest this plant as it is poisionous to both humans and animals...i'm a little tentative to feeding it to my chickens...although through alot of research have found out that it has many benificial properties...

just wondering if anyone has fed this to their chickens and what the results were....thanks

DJEB said...

Comfrey contains pyrrolizidine alkaloids, which accounds for the source of all the warnings. The roots contain the highest amounts of PAs - ten times the amount contained in young leaves - and old leaves actually contain less than the young ones. According to J A Pembery in the book The Safety of Comfrey, there were no medical records of people being poisoned by comfrey at the time of publishing. In the forward of the book, there is mention of one single pig that became ill after eating comfrey, and that was due to nitrate poisoning from the use of fertilisers on the comfrey. I could go on and on with studies that have looked into the safety of comfrey, found nothing, and walked away with the warning against comfrey still intact.

I've known people to use comfrey as a chicken fodder, and Isabell Shipard's book How Can I Use Herbs in My Daily Life? notes that "Trials show that the cost of processed foods for hens and pigs can be reduced 50% by the use of comfrey. Hens lay better, yolks have deeper colour, the vitamin B12 is higher, and the hens are healthier and more productive."

random planter said...

Thanks guys for a great informative blog - love those mindmaps.
I'm just getting into propagating comfrey because it is such a versatile plant.
The chickens do like it but I guess I have been holding back because of fears of poisoning them if I over do it.
I think I will gradually increase the amount I give them - it would be great if comfrey even supplied 25% of their requirements.

DJEB said...

Hi James,

First off, thanks for the link to Random Plantings! (And thanks for the link on Random Plantings to

I don't think comfrey will give you any problems. I wouldn't consume too much of it myself, but I haven't heard of it giving livestock any problems. On the contrary, I have heard many anecdotal accounts of comfrey helping medical conditions. The warnings are erring on the side of caution - not a bad thing to do, when you think about it. There just doesn't seem to be data to back the warnings.

Anonymous said...

am a woman with broken elbow (bike crash 6 wks ago) troubled by slow healing because of mineral absorption problems (post gastric bypass and rheumatoid arthritis).

I just got some comfrey plants . Can I just strip the wilted leaves off the stems and dry them on a cookie sheet in a warm oven (pilot light only)? Then crush, reconstitute with water and maybe a little olive oil or coconut oil to make poultices?

How would you handle it? I am a n00bie and would appreciate any advice!!

Julianne Wiley said...

am a woman with broken elbow (bike crash 6 wks ago) troubled by slow healing because of mineral absorption problems (post gastric bypass and rheumatoid arthritis).

I just got some comfrey plants . Can I just strip the wilted leaves off the stems and dry them on a cookie sheet in a warm oven (pilot light only)? Then crush, reconstitute with water and maybe a little olive oil or coconut oil to make poultices?

How would you handle it? I am a n00bie and would appreciate any advice!!

DJEB said...

That is a good question. I am only aware of people using poultices from fresh leaves.

I suspect your idea would be at least somewhat effective. I can't see any harm in trying it provided you don't have sensitive skin and/or allergies. If either are the case, you should (as always) seek the advice of a medical professional.

Wojciech Majda said...

"It is protein rich with reportedly 20 times the protein content of soy beans"

How can comfrey have 20 times more protein,than soy bean if soya bean have aproximitly 40% of protein (in dry weight).

If that would be true comfey would contain 800g of protein in 100 g of comfrey:) which would be a true solution to world hunger problem:)

Anyway I like your blog,

DJEB said...

That is a good question. I must mind my numeracy, regardless of what shows up in print. Cheers!