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Getting comfrey with growing my own fertilizer


Since I wrote this post, I estimate that I’ve watched more than 50 hours of British gardening shows. And I think I’ve learned more from them than I ever learned over all the years of watching American gardening shows. Some of that information—how to take cuttings, for instance—may not be completely practical as I have nowhere to overwinter delicate new plants, but it is fascinating information to know.
But until I watched a 2011 episode of “Gardener’s World” (one Youtube poster lists it as the “Best show in the world” and I wouldn’t argue with him), I had no idea that I’ve been missing out on growing my own fertilizer all this time. 
Apparently a small patch of comfrey will nourish your plants and kick your compost pile into high gear.
Until recently, my knowledge of comfrey was limited. I knew it was part of the borage family. I know that borage is a beautiful plant in an old-fashioned kind of way but also one that you never get rid of once you have it. I’ll be honest, plants like that scare me. I’ve had too many plants try to stage a bloodless coup in my garden (like these) and eradicating them is a chore that has taken years (and continues annually, in some cases). 
I also knew that I liked the name of the plant: comfrey. It sounds … well … comfy. It does have fuzzy leaves, so maybe it is sort of comfy (although it can be irritating to some people’s skin so maybe don’t curl up in a patch of it). 

But it turns out that comfrey is a little powerhouse of a plant. It can be used for medicinal purposes because it contains allantoin, which stimulates cell growth and repair, and as a high-protein animal feed, but that’s not why I’ve got my eye on it.

Nope, I’m interested in it because it’s a great fertilizer. Comfrey is high in potash, aka potassium (the “K” in NPK fertilizer ratios), which means it’s an excellent feed for overall plant health and particularly good for tomatoes and flowers later in the season. One source says that comfrey has more than twice as much potassium as farm manure and 30% more than compost. The NPK (nitrogen-phosporous-potassium) breakdown of comfrey leaves is 1.80-0.50-5.30 for true comfrey and that last number bumps up to 7.09 for Russian comfrey. On “Gardener’s World,” good ol’ Monty Don made comfrey tea and then watered his plants with it. He also used it as a foliar feed. And he used a big bunch of leaves as mulch for his tomatoes. Just slapped them right on there. They will feed the soil as they decompose. And anything that was left, including the stems, was thrown in the compost pile where it kick starts a pile that’s a little heavy on browns (i.e. carbon-based material). And another source claims that earthworm farms have found that adding comfrey to their worm beds increases worm numbers by 400%. Even if that’s an exaggeration, imagine what it could do for the worms in my compost bin.

You can also put a few leaves near plants prone to slug damage. Apparently it is so tasty to slugs that they will forego eating anything else in favor of attacking the comfrey.

How have I been missing out on all this goodness? It all sounds too good to be true.
Making comfrey tea is no more complicated that putting a lot of comfrey leaves in a bucket and covering them with water (some recipes say not to add water and just let them turn into sludge on their own). And then covering the whole thing with a lid or a board and stashing it away from human interaction for several weeks (a minimum of three seems to be the general consensus) while it creates a black, disgusting stew that apparently is extremely foul-smelling (hence why you don’t want to store it on your patio while it’s brewing). 
When it’s finished you strain it, dilute it with water  and pass the goodness onto your plants. The dilution rate varies, of course, depending on how strong your original batch is, but about 10 to 15 parts water to one part comfrey tea concentrate is probably a good goal.
It seems to be difficult to find plants, other than from other gardeners. I was surprised that our master gardener group doesn’t sell it at our annual heirloom plant and herb sale given that it’s such a useful plant, although I now realize that’s like because it can be fully thuggish if you grow a reseeding variety. So I ordered a few root cuttings, which it is said to grow from easily. That alone is a little scary. Any plant that grows well from root cuttings means that you better put it in a place that you like from the beginning because digging it out will be difficult. Unless you dig up all the roots, you’ll have more plants in that spot.

I ordered Russian comfrey (Symphytum x uplandicum), a variety called Bocking 14, which is said to be sterile, so at least I don’t have to worry about it reseeding all over the place,  although cutting off the flowers before they set seed would also work (this is so much easier said than done). Apparently it is best to use it before it flowers, or right as it starts flowering. This strain is not great for animal feed—apparently it is more bitter than other strains—so I’m hoping that it won’t be tasty to deer.

I’m going to find a little patch that’s out of the way. I’m still worried about it getting aggressive, but I think if I can provide it a nice little spot away from the main garden areas, I can let it be true to its nature.

Growing my own fertilizer: what could be better? I’m becoming a more self-reliant gardener, recycling in my own yard and saving money in the process.

Comfrey, here I come.

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23 Responses

  1. You got me started on Gardener's World and my life has changed. I actually take notes when I watch it! So much more informative than anything on American TV, and great supplemental information that wasn't covered in my Master Gardener training. So, THANKS!

    Here's a thought about the comfrey spreading, what if you treated it a bit like bamboo and circled the plant/area with some buried metal flashing about 6-8" down, that might prevent/slow any crazy root growth and would give you a clear area to shovel out if you ever want to get rid of it? Either way, comfrey is coming into my garden too!

    1. I'm so glad to hear that I'm not the only one entranced by "Gardener's World." That's a good idea about containing it and maybe I'll try that. Or maybe I'll just go for it in an out of the way area. I better decide soon because I'm hoping my root cuttings arrive next week.

    2. Cortney turned me on to Gardeners World and to you, Erin. We are in the process of buying a home in PA with a pretty blech garden, and will be referring to you over and over and over.

  2. Count me as another you have gotten addicted to the British gardening shows. I love that they have dirt under their non perfect nails and actually work in the rain. I learn something from every show I watch. *Theresa from Ohio*

  3. I'll have to look that episode up! My mom has been growing comfrey for years and I knew it was a beneficial plant, but I never knew you could make fertilizer from it! I'll have to see if she has a root or two to share. As you suspect it does have a prolific nature so I'm glad to hear you are taking precautions…it is such a pretty plant though and bees absolutely love it so it is worth it!

  4. It truly is the best gardening show in the world! I, too. Learn something new every time I watch it. But I missed this episode! Think I'll try and find some comfrey and plant it right in my vegetable garden! Thanks for the tip.

  5. I need to start watching these shows! (Like I need another addiction.) BTW, have you ever planted Japanese Anemone? Talk about invasive and hard as heck to pull up. Never heard of comfrey – thanks for the intro, Erin. It's always fabulous to visit the blogs of garden friends.
    Cheers and have a wonderful Easter weekend!

    1. Loi, and Erin: I've grown Japanese Anemone for years and in various gardens. Yes, it spreads…nicely, I think!…but I don't really see it as invasive! I also happen to love it, both in pink and white, so don't really mind if it spreads!

  6. i have not grown it but all my gardening friends in england do and use it like mentioned. foul? there are no words to describe the scent, but what results!
    think i need to rethink this, thanks for the reminder!

  7. I always have a tub of comfrey mixed with nettles brewing away near my vegetable patch. It is wonderful stuff but oh dear! The smell is absolutely disgusting.

  8. I know next to nothing about gardening, but it seem to me that if comfrey has lots of potassium, growing it would pull potassium out of the soil, right? So I guess if you're growing it in an out of the way area where you don't need the potassium in the soil to nourish other plants, that works okay, but otherwise, it seems like it would be a zero-sum proposition?

    1. I don’t think it pulls potassium out of the soil , it makes it while it grows and can be used to add potassium to the rest of the garden

  9. I grow ‘comfrey’ here on the island of Montreal. I got a plant while foraging in Hudson, that’s a pretty English town off the island just west of here. I simply brought it home because I found it to be an interesting plant. The bees can’t get enough of it. Thank you for enlightening me! It sure is a hardy plant. My flowers do go to seed. Beautiful teeny tiny dark metallic balls. I really don’t know if those grow or not. After it flowers and is no longer any use to the bees I slash it down as the leaves are quite coarse, rough on raw skin. I’m a Forest Technician and so glad I discovered it! Happy re-forestation!

  10. Comfrey is amazing ! Plant at bottom of fruit trees and it mines the minerals from deep in the soil and draws them up to the surface feeding the shallow roots of the trees. Then with frosts it breaks down to a natural mulch which feeds the tree over winter as it breaks down . I make comfrey oil also which I use in all my healing balms as it’s incredible for rejuvenation of cells in our bodies also. It’s old nickname is ‘knitbone’ It’s great for thinning hair ( I make a hydrosol from it mixed with rosemary for that …
    Enjoy your comfrey

  11. Comfrey makes a fantastic plant food, after all anything that’s smells so disgusting whilst fermenting must be really good. It is a thug, but the bees love it so I forgive it anything. I ferment it, chop it up and add to my beds and my compost heap. Living in England I (and everyone else) follow Gardeners World and the brilliant Monty Don. He’s a proper gardener. Keep gardening folks and good luck.

  12. My bocking 14 wasn’t aggressive and didnt spread much, chopped it down 2 to 3 times a year, the bees love it.
    I put the leaves in a drain pipe with mesh at the bottom and a 2 litre coke bottle taped to the drain pipe and a weighted jam jar on top of the leaves and a lid on top, the juice collected in the bottom to use as a feed and it didnt smell!

  13. This is very informative and very helpful for anyone that is worried about the rising cost of fertilizer on his/her garden and farm generally, especially, for those in the developing world. I’ve just placed my bocking 14 comfrey roots for planting this farming season.

    Thanks Erin for your contributions.

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