Comfrey ways to eliminate it?

After planting one small comfrey  10 years ago it is taking over my backyard where I grow vegetables. Is there any natural way to eliminate it? I was thinking sheet mulch might work but the roots are so very deep it might not. What do you recommend?

In order to eliminate it, comfrey needs to not be able to see the sun.

Sheet mulch, or a deep layer of mulch and wood chips might do that.

I used a piece of scrap plywood, placed on top. Then mulch over that. Mulch alone won't do it, as the comfrey is robust enough to push through a deep layer of it. You might find cardboard works, but with such a vigorous root system, I would probably want something sturdier.  When it is dead just take the ply away and reuse it for killing something else off.

I keep seeing information about planting comfrey under apple trees to bring up minerals so I researched it and found it is a nightmare invasive weed.  It can be beneficial but folks better want it everywhere.  With the deep roots, you can't pull it up and it will just keep coming back.  

Do you know which comfrey you have? The wild kind that produces fertile seeds has a reputation for spreading like that. Plus all comfrey seems to get a bad rap from people who tried to wipe it out by tilling. The bocking varieties (#4 and #14 are popular) are sterile. I'm only three or four years in, but mine only gets bigger, but has never gone more than eight inches or so from where I planted it. (A tiller still won't get rid of it. Any root piece an inch or so in length is likely to become a new plant.)

I have comfrey on two different sites.

1) In Wales, where there is lots of rainfall and a high water table. It is planted around an apple tree and does an amazing job. It grows vigorously, shades out all the grass and weeds around the tree, and the tree is thriving.  The soil beneath the comfrey is black, moist and full of organic matter. The comfrey has stayed where it was planted.

2) At home in Kent. Less rainfall, chalk soil that are very free draining, low soil moisture through summer. The comfrey grows slowly, and is no where near as vigorous as Wales. They are the same variety, propagated form the same root stock. It doesn't effectively suppress weeds, but does feed the soil somewhat. It stays put there, without any invasive tendencies. I think the water is the key issue, and if I were to irrigate my growing areas in Kent the comfrey would probably thrive.

Michael Cox wrote:I have comfrey on two different sites.

1) In Wales, where there is lots of rainfall and a high water table. It is planted around an apple tree and does an amazing job. It grows vigorously, shades out all the grass and weeds around the tree, and the tree is thriving.  The soil beneath the comfrey is black, moist and full of organic matter. The comfrey has stayed where it was planted.

2) At home in Kent. Less rainfall, chalk soil that are very free draining, low soil moisture through summer. The comfrey grows slowly, and is no where near as vigorous as Wales. They are the same variety, propagated form the same root stock. It doesn't effectively suppress weeds, but does feed the soil somewhat. It stays put there, without any invasive tendencies. I think the water is the key issue, and if I were to irrigate my growing areas in Kent the comfrey would probably thrive.

I agree with this as I live in the high desert of southern Utah and unless I regularly/daily irrigate nothing other than native desert plants will grow.  Consider your area and climate if you think you want to grow comfrey.  For me it is not invasive.  It may eventually take over my raised bed but for now I can still plant other herbs and veggies there.  If it does take over out birds will love it as a regular snack and we will move our herbs and veggies to another area.

Building a hot compost pile on a comfrey plant will kill it too, but if a large portion of your yard is covered by it, solarizing may be the only good solution.

This is the reason I've always resisted the urge to bring in comfrey.

Even the non-seeding varieties will eventually spread out.

Someday I will leave this land or die. You, too, might not be taking care of your land and your Bocking comfrey forever. I don't till, but the next person might. I hope they don't curse my name for the things I planted or built...

Hello - never posted here before.
Reading everything I can about eradicating comfrey.

We didn't know about the sterile variety and we went all in planting two massive rows of the stuff about three years ago. Last year, I chopped and dropped about 6 times over the season and lay all the leaf mulch around fruit trees. I appreciate all the nutrients but I can't stay on top of the harvest and it's spreading into other parts of the garden (seeds) so we want to kill it dead, even if it means we lose that growing space.

I saw the comment about covering with plywood and wondered how long it takes for it to kill the comfrey and, given there is a substantial and strong root underneath, if there is any chance it could come back once the ply is removed? Sadly, we are talking about a substantial area so I need big solutions - we have some scrap metal sheets and silage tarp that we are hoping to use for this endeavour.

Bed 1 - about 30 plants sandwiched between a dense planting of sun chokes on one side and herbs for tea on the other (lemon balm, hyssop, bee balm). (about a 40 foot row)
We had some sheets of old metal roofing so I've covered the row with that and weighed it down with logs. I am planning to leave that row of metal in place for at least a year, maybe two, but would leave it longer if there is a chance that the comfrey will come back from the roots. Thoughts?

Row 2 - this one is trickier. We planted another 12-15 comfrey plants along a row of hazelberts. The seeds clearly dropped and there are millions of baby comfreys coming up all over the bed! The best I can come up with is trying to dig up the hazelberts, shake off all soil, and transplant them (to where I don't know) and cover the entire bed in silage tarp for one or two years. Or, we can try to leave the hazels in place and cover the bed in either black bio plastic or silage tarp and do our best to cover all the comfrey and leave the hazels exposed, but I'm worried about the efficacy of this and whether the heat / solarization of the bed will ultimately harm the hazel roots anyway. This is another massive 'bed' about 5 feet wide and 40-50feet long. It's got grass that gets mowed on one side and sedge/reeds/ marsh grass on the other so I suspect that the comfrey shouldn't have much success outside the bed.

Anyway, thank you for reading. This feels like one of those big and painful gardening lessons that we just had to learn (research varieties and start small!!!) but I would love to tackle it and regain those growing spaces one day if possible. Your advice and insights are greatly appreciated!

JJ

Dig it up and sell it on Etsy.

People are buying it...

j

If you follow that advice you better tell people what kind it is. 99.9% of people do NOT want the kind that spreads by seed. This is why I found a reputable business with tons of referrals on here to insure I got a sterile variety.

Jay Dev wrote:Hello - never posted here before.
Reading everything I can about eradicating comfrey.

I saw the comment about covering with plywood and wondered how long it takes for it to kill the comfrey and, given there is a substantial and strong root underneath, if there is any chance it could come back once the ply is removed? Sadly, we are talking about a substantial area so I need big solutions - we have some scrap metal sheets and silage tarp that we are hoping to use for this endeavour.

I dug up some comfrey in a spot I didn’t want it this last month. (Only a small amount, not what you’d want to do!) HOWEVER, what is relevant for you—I did notice that some of the comfrey roots had rotted. Comfrey above ground also rots very fast and the roots had broken down into black mush. If I had my guess, comfrey roots would not take too long to die and disintegrate once the leafy part could not photosynthesize.

But as someone else said, it would need a thick impermeable barrier like a piece of wood. I have comfrey coming up in my yard through a foot of mulch, two feet of dirt. I was digging a foot or so down and found a blanched comfrey leaf punching its way up through the soil.

I read somewhere on here that comfrey is hard to propagate by seed. Something like 10 percent will grow. I'm sure that varies by zone. But is 10 percent that much more? Perhaps over time. I'd be cognizant of where the original plantings were, and hopefully mow the rest of it down. Maybe not the perfect solution, but anything that spreads by rhizome is going to have to be looked after with a keen eye.

j

 

Joe Hallmark wrote:If you follow that advice you better tell people what kind it is. 99.9% of people do NOT want the kind that spreads by seed. This is why I found a reputable business with tons of referrals on here to insure I got a sterile variety.

This person just said millions are coming up from seed. Anyways. If you intend to sell any plant it is best to describe it very thoroughly. If it’s a nightmare for you there’s a very good chance it will be the same for the next person.