Is Comfrey Bad for You?

Yes and no. Comfrey uses and benefits are many, varied and somewhat conflicted. A quick superficial search indicates that comfrey is dangerous and toxic.

While comfrey has been used for centuries as an internal and external medicine, it’s not without potentially lethal consequences, depending on the health of the individual and the amount they are ingesting over time.

Most studies indicate the health issues from consuming comfrey were the result of excessive consumption. That’s often the case with herbs, where — as with medicine and pretty much anything in excess — too much of a good thing is no longer good.

So with comfrey — as with all medicinal use of herbs and plants — it’s important to use after careful research and guidance from the appropriate trained herbal health care practitioners.

There’s no need to take the risk when there are plenty of other remedies you can use. However, when it comes to comfrey, there are plenty of safe external applications for your garden and your body, which we will get into in this article.

The Good News – Safe Comfrey

There are licensed medicinal products available today that contain depleted or pyrrolizidine alkaloid (PA) free processed extracts. However it’s hard to find internal medicinal extracts, likely in order to be absolutely safe from possible liability issues.

There is some concern over the possibility of absorption of externally applied products, and to that end there are some external comfrey ointment, salves and creams that have removed the toxic PA. And of course if you’re growing comfrey, you can make your own.

Scientific Research on Consumption of Comfrey

Pyrrolizidine alkaloid-containing plants are probably the most common poisonous plants that affect livestock, wildlife, and humans. Comfrey is a PA-containing herbal plant that exhibits both therapeutic and toxicological activities. Although there are no epidemiological data regarding the carcinogenicity of comfrey, there are a number of cases that implicate human consumption of comfrey in the development of liver diseases.
~Nan Mei, et al, PubMed study on comfrey toxicity

Beneficial uses of comfrey are many. For safety, seek appropriate health counsel or use externally.

The Incredible Comfrey

Comfrey is one of the most beneficial plants and weeds you can use for compost tea. In fact, our plants love comfrey compost tea, and it’s one of our favorites, especially since we have so much of it flourishing. We’re all in favor of some of the best fertilizer ever… for free!

Comfrey is an amazing plant but unless you get the Russian variety, it can take over your garden! We didn’t know that when we first planted ours, but now that we use it regularly to nourish our garden, it all works out.

We have plenty for nutritional and medicinal use for ourselves as well as our garden compost and compost tea, plus enough to give away. At first we were bummed that we did not get the non-invasive Russian comfrey, but now we’re glad because the common comfrey one we’re growing can also be used medicinally as well as for organic fertilizer for plants.

What Are Common Names for Comfrey?

1. Knitbone
2. Boneset
3. Bruisewort
4. Black wort
5. Salsify (which is actually a different plant: Tragopogon porrifolius, a purple-flowered, composite plant)
6. Ass ear
7. Wall wort
8. Slippery root
9. Gum plant
10. Healing herb
11. Consound
12. Knit back

Comfrey Facts

Comfrey is an amazing plant whose roots can grow as deep as 20-30 feet! Comfrey’s incredible root system is the reason it has so many nutritional and medicinal benefits for plants and humans.

• Botanical Name – Symphytum
• Nutrients –
  • Mineral rich
  • One of few plants containing vitamin B12
• Origin – native to Europe and the Asian countries of Caucasus, Kazakhstan, Siberia, and Turkey; now naturalized worldwide
• Herb – dubbed ‘a miracle herb’
• Roots – very deep roots (20-30 feet)
• Invasive – non-clumping comfrey varieties can be very prolific and invasive
• Family – Boraginaceae, including borage (Borago sp.) and heliotrope (Heliotropium sp.).
• Genus Symphytum, contains ~35 species

Growing Comfrey

• Appearance – thick furry leaves
• Frost resistant
• Difficulty – easy growing
• Size – 12-36″ tall and 9-30″ wide, (Russian comfrey can grow up to 6′)
• Soil –
  • loamy, well-drained
  • moisture – even moisture preferred
  • pH – Neutral (6.0 to 7.0)
• Drought tolerance – moderate drought resistance once established
• Sun – Full sun to partial shade, (more shade for protection in warmer zones)
• Plant Type: Herbaceous perennial
• Zone – USDA Hardiness Zones 3-9

Common Varieties of Comfrey

• Caucasian comfrey, Symphytum caucasicum: This plant is commonly referred to as or blue comfrey for its flowers that start pink but then transition to a bright blue.
• Common comfrey (Symphytum officinale)

Best Comfrey for Gardening

These comfrey plants are best for garden uses and to avoid consuming internally due to a higher pyrrolizidine alkaloid content that can be toxic. The Russian variety is favored for its clumping, non invasiveness.

• Russian comfrey (Symphytum x uplandicum), clumping, non-invasive, can grow 6′ tall!
• Prickly comfrey or (Symphytum asperum)
• Bocking 14 cultivar of Russian Comfrey, Symphytum x uplandicum, European Symphytum officinalis, is a clumping variety that does not produce seeds.

Best Comfrey for Medicinal Uses

• Common comfrey, Symphytum Officinale: most often used for health and healing benefits
• Cover comfrey, Symphytum grandiflorum: Known commonly as large-flowered comfrey or ground cover comfrey, this plant features showy cream to white blooms. 

Comfrey’s deep roots and big leaves means deep mining for—and storage of—minerals and trace nutrients.

COMFREY USES

Comfrey Uses in the Garden

• A green fertilizer – Chopped leaves placed around your plants
  • Compost activator – as a liquid fertilizer ‘comfrey tea’
  • Water soluble fertilizer – delivers nutrients more evenly and avoids chemical burn^[1]https://www.extension.purdue.edu/extmedia/ho/ho-251-w.pdf
• Anti-fungal – Contains copper, beneficial as an antifungal and antiviral plant spray
  • Powdery Mildew – helps prevent and/or treat

Comfrey Compost Tea Recipe

• Fill container ~3/4 full with chopped or torn large comfrey leaves (we use a 5 gallon bucket)
• Add water to the top
• Steep for ~2 weeks until leaves rot (we cover ours loosely with a board)

Instructions:

After leaves are rotted:

• Stir, then pour half into another bucket
• Add water to both buckets until mix is a weak tea color, (you now have double the amount)
• Pour around the roots of your plants, (we pour from the 5 gal. into a garden watering can with the “rose” spout removed.

Immediately Start a new batch.

Once this batch is ready, go ahead and start your next batch to steep for two weeks. That way you will have enough to water your plants every week or two with compost tea, and watch your plants thrive! If you have a large garden and lots of plants, then double your quantity and/or frequency.

We’ve written more and included videos on making compost tea here.

While visiting one of our favorite growers, Edible Landscaping, in Virginia, we enjoyed a tour by the manager, George Dean. George has worked with plants all his life, including for the Reagan Whitehouse greenhouse, and is a walking book of plant knowledge

We thoroughly enjoyed his tour expounding on the many benefits of comfrey, amongst many other plants. Here’s his take.

Comfrey Compost Tea Recipe – SIMPLE Old Timey

Less smelly, this time-tested process is even simpler. You’ll just need to buy or make a dispensing bucket with a spigot or tap at the bottom, or a top pump that siphons it from the bottom.

• Fill a container with chopped comfrey leaves
• Place lid or weight (we use a couple bricks on top of plywood cutout)
• The lid doesn’t need to be tight but you’ll want to keep it out of the rain
• NO WATER

The leaves should break down in a couple weeks but without the unpleasantly potent odor resembling dead fish. In a couple weeks or so, you’ll have a black fermented comfrey tea concentrate.

• Dilute 1 part comfrey concentrate to 20 parts water for container plants and seedlings
• Dilute 1 part comfrey concentrate to 10 parts water for garden and larger plants

If you have any extra compost tea, store in a jar in a cool dark place or refrigerator. Just be sure to mark it as COMFREY for the GARDEN, to keep anyone from accidentally consuming it or tossing it because it smells like something gone bad. I mean… it is fertilizer, after all!

Dangers of Comfrey

Remember, illness and even death has occurred from uneducated use of medicinal plants such as comfrey, the same as with any medicine. So best to utilize comfrey for some of the proven externally applied benefits, or under the counsel of an herbal practitioner.

Best Comfrey for Plants – Russian Comfrey, Symphytum x uplandicum

Any comfrey is good for your garden, but Russian comfrey, Symphytum x uplandicum, has been found to have the greatest benefit for plants. This non-spreading form of comfrey is superfood for your plants.

Contribution From the Community

“Include some Russian Comfrey Blocking #14 strain (clumper) along the base, too, to bring up soil nutrients from it’s deep tap root. IMPORTANT to use a clumping variety of Comfrey; other common types are invasive. Comfrey will die & self mulch in place during fall. Over a period of seasons, the soil around the trees will become loamy. During it’s green growing season, it shades the base of fruit trees, conserving ground moisture intended for the fruit trees (see espalier fruit trees). First, the daffodils (see deer resistant flowers) will bloom then shrink, about the time the Comfrey starts to poke out from the ground.
~Kelly S. Bracken, retired, permaculture design certified

Dangerous Look-alike Plants

The leaves of comfrey resemble those of foxglove (Digitalis purpurea), and this mistaken identity is even more likely to occur when the plants are not in bloom.^[2]https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/comfrey

Cardiac glycoside poisoning^[3]https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/glycoside can occur when people confuse foxglove (Digitalis purpurea) for the comfrey plant, (Symphytum officinale).

Most of the toxic issues involving plants and herbs in health and healing, including comfrey, is mostly a matter of absence of knowledge. Fatal cases involving comfrey typically includes excessive or prolonged consumption by people with existing conditions or proclivities.^[4]https://www.henriettes-herb.com/faqs/medi-2-15-comfrey.html

People tend to forget that plants—especially herbs—contain high concentrations of medicinal substances, which require small doses. At high doses most any medicine or herb can become toxic. As such, it’s best to take doses and remedies in quantities and preparations recommended by health professionals and herbalists.

Safe Substitutes for Comfrey

• Calendula – wounds
• Plantago – wounds, coughs

REMEMBER: Always use caution and guidance in using this or anymedicinal herb.

“Wild common comfrey, Symphytum officinale, has been cultivated since about 400 BC as a healing herb.“
~Purdue University

Comfrey Uses for People

The comfrey used for medicinal use is the common comfrey, Symphytum officinale. Symphytum is Latin meaning ‘growing together of bones (Greek ‘symphis’), and phyton for plant.

Remember, “medicinal”, means taken carefully, judiciously and under guidance. Informed and limited consumption and application of common comfrey has been used for millennia. However, today’s recommendations are for careful and conscientious external application.

Proven Health Benefits of Comfrey – Applied Externally

Wounds and burns seemed to heal faster thanks to the allantoin content in comfrey.

• Anti-inflammatory
• broken bones
• bruises
• burns
• wounds
• sores
• sprains
• strains
• swollen tissue
• Healthy skin – mucilage content
  • moisturizes
  • soothes
  • regenerates – increase in cell multiplication (allantoin)

The German Commission E has assessed Symphyti radix (comfrey root) deriving from Symphytum officinale L. positively for external use.

~Kommission E. Monographie Symphyti radix (Beinwellwurzel). Bundesanzeiger No. 318. 1990 July 27.^[5]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3580139/#CR8

But what forms are most common comfrey uses?

You can make your own comfrey extract for use in salves, creams and oils.

How to Make Comfrey Extract

1. Fill a jar with chopped comfrey leaves (cleaned and spun dry using a salad spinner)

How to Use Comfrey

My favorite daily tonics include; nettle, comfrey, rosemary, oats, lemon balm, hawthorn, dandelion and burdock. 
~Rosemary Gladstar, herbalist, author

“We all learn at the humble roots of the plants…all the way back to the beginning of time. Let’s not forget how to listen, how to hear, their language. It is not a lost language, or languages as they speak in many tongues, but a forgotten language that is heard with the heart.”

~Rosemary Gladstar, herbalist, author

To Divide Comfrey

It isn’t easy to divide comfrey, for it has a long taproot, similar to other medicinal plants like dandelion and balloon flower.

We’ve found the best way to divide and transplant comfrey is to:

1. Use a long spade shovel
2. Dig the younger/smaller plants for their taproot isn’t as deep and so they come up easier.
3. In future, and if we had it to do again we would:
   • plant the spreading comfrey in pots
   • plant the clumping comfrey in the ground.

Wishing you great gardens and happy harvests!