The Walden Effect: Farming, simple living, permaculture, and invention.

Comfrey is hard to kill

Hugelkultur kill mulchLast year, I decided that the comfrey I had planted underneath my nectarine was competing with the tree for nutrients and had to go.  I waited until the fall, then laid down a layer of cardboard topped with punky wood, compost, and wood chip mulch.  Surely, I thought, the comfrey will die under such a serious kill mulch.

"Hi there!" the comfrey called last week as it poked its way up between seams in the cardboard.  "Such a nice spring!" added another comfrey plant that had moved an entire Invading comfreylog aside to make way for its new growth. 

Folks who warned me that comfrey is hard to kill were entirely right.
  If you're thinking of some comfrey interplantings, take heed --- once you put comfrey in a location, it's there to stay.

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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comfrey is an excellent plant. its great that you planted it under your fruit trees. the roots on comfrey go deep, pulling up many trace nutrients making them available, through decomposition, to your fruit trees shallower roots. i wouldn't fret about that being there, just harvest to the ground more often. trust me, over the years the benefit will be there, as well as the benefit from the decomposing mulch. you're gonna have a worm haven right where you want it to be.
Comment by eric Tue Mar 29 09:41:35 2011
Yep, I've read all that, and that's why I put the comfrey there. However, I think we have to be aware that sometimes real life conditions don't match what we read. The area where that nectarine is living is poor soil --- it gets waterlogged, so I suspect neither the tree nor the comfrey can put many roots too deep. I suspect that in well-drained, rich soil, the comfrey and the tree might be able to coexist better, or perhaps if the tree was older and had a better root system. I have some comfrey under my biggest peach and there the comfrey doesn't seem to be harming the tree --- the tree was so big when I put the comfrey in that it shades the comfrey down to a relatively small size. But in poor soil, I think the tree has to work too hard to get nutrients to be able to outcompete comfrey, and the comfrey takes more than its fair share.
Comment by anna Tue Mar 29 11:57:00 2011
I have read about how good comfrey is as a livestock feed, and certainly a good green manure. I think that even chickens will eat it. I have tried to find places where I can get starts or seeds, but because it is so invasive, I suspect that most gardening companies don't want to carry it.
Comment by David Tue Mar 29 12:01:46 2011
I'm still sold on comfrey, just keeping it away from my most needy trees. Actually, I've considered planting a whole mass of it to mow for mulch, but have get to get around to it. If I did that, I'd probably hunt down the Russian comfrey that's supposed to be so good.
Comment by anna Tue Mar 29 16:44:34 2011

Curious what you are seeing that tells you the two are competing for nutrients? Do you think it could also be just the water logging causing the issue?

You might consider not putting so much mulch down as it will not allow the area to dry out periodically.

Also, I would recommend mulching the tree with green manure from vetches and yarrow for additional nutrient accumulation, especially Copper. Could maybe plant some Bracken fern around there for the same reason.

sorry for the unsolicited advice. keep up the great work. ;)

Comment by eric Tue Mar 29 18:44:13 2011

I've got several fruit trees growing in the waterlogged area, but only have comfrey under one, and that's the only tree that showed signs of lack of nitrogen (yellowing foliage) last year. In that area, I plant the trees in raised beds, so they're not actually waterlogged and, if anything, get a bit dry, thus the mulch. It's a bit like growing a tree in a pot, though, because the main soil beneath the raised bed is often too wet for growth.

I generally keep the green mulches for the vegetable garden since they promote bacterial dominance in the soil. Using woody mulches for trees promotes fungal dominance, which is generally appreciated by trees and shrubs. If I was lacking a certain nutrient, though, I'd be sure to mulch with a dynamic accumulator of that nutrient.

Comment by anna Tue Mar 29 19:58:03 2011

If you are still interested in the Bocking 14, I found root cuttings available at this site:

I was all ready to purchase them, but then read about how invasive it can be and I'm not sure if I'm ready for any more invasive plants right now. I suppose that works in its favor if you can keep up with the maintenance, but I have seen what happens with aggressive garden plants after the original gardeners get old and leave them behind... and it's not pretty.

Comment by Sara Sun May 8 01:34:14 2011
I may have to do that! I figure invasive isn't a problem if I choose just the right area where I can mow it regularly to turn into mulch. You've got a good point about if the original owners leave, but I've never heard that comfrey turns invasive in a wild environment, have you? I think it's really just a very keen garden competitor.
Comment by anna Sun May 8 11:08:31 2011

The only evidence I have that it might be invasive in wild areas is anecdotal, and perhaps based on fear. Also, I'm not sure exactly which plant, and I think the invasiveness of the hybrid is still uncertain.

It sounds like a great plant, but I don't really have a good plan to control it and I'd hate to be overwhelmed by something that I thought would be beneficial.

Comment by Sara Sun May 8 14:42:19 2011
My understanding is that the hybrid variety isn't supposed to have viable seed, which means it can only spread by division of the roots. Granted, comfrey is quite good at spreading that way, but that does mean that the comfrey isn't likely to hop over to wild areas and take root. I guess it's a bit like running bamboos that way --- while they can be highly invasive in a specific area and impossible to eradicate, they can't really take over the world like kudzu.
Comment by anna Sun May 8 16:59:50 2011

I have neighbors who have planted comfrey and other deep-rooting plants at the side of their house. They now have serious basement leak problems maybe not caused by comfrey and these other plants, but certainly exacerbated by them.

I write this because this afternoon I decided to remove a comfrey plant I had moved from one side of my garden -- next to the aforementioned neighbors -- to the other. The plant is not all that mature, but when I dug up the root, I was stunned. A plant that last year grew only about a foot high had the roots of a seven foot tree, and the center of the root bundle was the size of my fist.

Comfrey is a serious threat to other plants, primarily because it grows so fast and has a broad leaf-span. and ends up overshadowing other slower-growing plants. However, I think one should take note that such a large root structure cannot be good for other plants in the vicinity. I have a large plot of heliotropes, and while their root systems are far reaching and invasive, they are nowhere near a large as those of comfrey, and are easy to eliminate.

Comfrey is also a threat to foundations, patios and driveways because of its large powerful roots, and its ability to grow just about anywhere that has a decent amount of sun.

Because of my neighbors' failure to control their comfrey, I have plants growing all over my property, and too near my driveway. Sooner or later I am going to have to take the neighbors to task over this, because, while the driveway is one thing, sooner or later the comfrey is going to get too close to my foundation and present a serious problem. And, as I noted, digging this stuff up takes a great deal of effort.

Btw, the big joke RE this is that my neighbors lodged a bylaw complaint about my ornamental grasses (which was quickly quashed), which are far less invasive and destructive than their comfrey.

Comment by Sebastian Wed May 15 22:07:40 2013
I have a bad property abutter.Has bad standing in the town for many reasons. My least irritating concern regards, "Lou".. He has a big patch of invasive comfrey. It has jumped the property line, wide stone wall, and over the last 3 years I've had to mount serious attack on it, which I do with a weed wacker. Given it's watery tropical-like structure, I am covered from head to toe with wet pieces of the plant & have to leave my clothes outside & shower immediately after an attack. And that doesn't get rid of the awful stuff. I will try some suggestions for killing it here on this site. Thanks.(I could put down big black plastic strip but that might kill all the big maple shade trees on the same line. One of your posts here suggested that someone was thinking about taking task (legal) with an abutter who let his comfrey go wild. Is there such a legal pursuit available ? Can you tell of it? Thank you in advance.
Comment by Maxine W. Snow Sun Jun 5 10:44:02 2016

Sounds like u guys have a bigger problem with stress than with comfrey.

Just pull it out. If it's somewhere where you don't want anything to ever grow then salt the ground

Comment by John Wed May 27 09:57:07 2020

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