**Major edit here**. If you are really interested in having healthy blueberries, please disregard the rest of the information in this particular post. Keep reading the thread and you will find out why.
So if you are interested I would say go for it. I might try this with my blueberries as well. Like you, I would like some weed control also. I think the route I will use will be to first mow/trim right to the soil surface. Next I will lay down either some old cardboard or tests (I am a teacher) as a sort of organic weed barrier. Next I will lay down a nice layer of wood chips. Finally I will get some comfrey roots and poke them into the soil (though it is probably not necessary, I will likely poke a hole through the weed barrier where I intend to plant).
When I first grew comfrey I planted into a topsoil/manure/bat guano mix as I had been advised that comfrey grows best with lots of nitrogen. This is true for comfrey after about a year, but not necessary for establishing comfrey. Now I fertilize comfrey once or twice a year with urine.
As the comfrey grows, add more chips and both your comfrey and blueberries will all be happy and healthy.
Good luck and let us know how things work out for you.
Fair points Redhawk. I have heard of comfrey being planted around other fruit trees/bushes. I had not thought it would become competitive with the blueberries. I get the ph issue. Can you shed some light on why comfrey is apparently helpful for other fruits but not so with blueberries?
I think it has to do mostly with the depth of the roots of the fruit bush/tree and the acidity requirements.
Three years ago I planted blueberries in an area I had grown comfrey in and when I checked the pH it was about right for blueberries (6.2) so I planted five low bush plants of two varieties and acidified the soil so my reading was 5.3 pH.
Thinking I was good to go, I removed the comfrey tops and made sure the blueberries were 3 feet from the closest comfrey crowns.
I checked the pH at the berry root ball 3 months later when I noticed they weren't looking healthy and the pH was 5.9, so I added another acidity adjustment and in two weeks the berries looked like they were recovering fairly well.
two months later, another pH check showed that once again the pH had risen to almost 6.0 and once again the bushes were distressed. (I had not even thought about the amount of N being used by the comfrey at that point)
Two months later the bushes began to die out from the growing tips and no matter what I did to the pH, they continued to die until they were gone.
This led me to do some extensive testing and I discovered that the pH in that area was at 6.3, nitrogen was low as was phosphorus, which the berries need for overall health.
I checked an area within 10 feet of the dead berries and the pH was 6.8, minerals were all in a high acceptable range and most importantly, there wasn't any comfrey any closer than 13 feet.
This year I have planted new high bush and low bush blueberries in a totally different and distant spot from that first, failed attempt, there isn't and never has been any comfrey in the new area. (and won't be)
I'm still testing the effects of comfrey, but it does great around my apple, peach and pear trees and the hogs love to eat down the comfrey I planted in their fenced in area.
I've read quite a few studies of comfrey but still haven't come to any hard and fast conclusions, except that for most plants that like a "normal" pH and aren't heavy feeders, comfrey does a lot more good than harm.
Not to mention that most farm animals seem to love to eat it.
I don't really classify it as competitive with blueberries, I am more thinking it is detrimental to the proper growing conditions that blueberries in particular need to thrive.
I am fairly certain that my first plantings died from being over stressed rather than being out competed.
That was extremely informative, and somewhat counterintuitive. I would have assumed (as apparently you did as well) assume that comfrey would have been a good companion plant. But apparently not. I guess I will keep my comfrey away from my blueberries. Would the leaves still be good to bring in for chop&drop, assuming I don’t bring in any stem that might root into the soil?
If I have extra chips (and I think I will) I will likely still lay down a nice layer of wood chips, and I might try starting off some wine caps. But thanks mightily for the warning.
I see no reason to not use comfrey leaves and woodchips for a mulch. I'm not trying to get people to not try planting near comfrey, just to be aware that there could be issues and to watch close the development of the blueberries.
I'm still trying to discover what happened to my first ones, but the current evidence points to my comfrey as being at least one of the culprits to the bushes demise. (I checked to see if some sort of cutworm might have been involved but there were none)
This year will give me more data and then I'll be doing more testing of the first area since it is now almost all comfrey.
It is also possible that there would be no serious effects on established blueberry bushes.
I found some wild huckleberries on an abandoned site where comfrey was intermingled with the huckleberry bushes and even though they don't have many leaves right now, the bushes have a massive amount of swelling buds and flowers.
I don't know when the comfrey was planted or if it is a volunteer situation but I did bring back some soil samples and plant material samples for testing.
I'm also making the addition of mycorrhizae in two rounds on my new bushes, my thinking there is that a lack of proper mycorrhizae could have been at least part of my first try problems.
I'm growing lupines near a couple of my blue berry bushes. I just chop and drop them when they get too big. The blue berries have been in less than a year but so far seem to be doing fine--got a good harvest of berries last year. But my blue berries are a southern variety that does better with higher pH than standard blue berry bushes. They also do better in areas with warmer winters.
Lupines get big taproots and are also nitrogen fixers. I'm using them around a lot of my trees and shrubs and so far it seems to be working.
I use a couple different native varieties but there are a ton of lupines to choose from.
I wouldn't put comfrey next to the blueberries, nor rhubarb. Rhubarb has a deep taproot--like comfrey--and is acid loveing--unlike comftry. But it spreads wide. Even with chopping and dropping my rhubarb, it still killed two blueberries in a row that had the misfortune of being planted too close to the rhubarb. Rhubarb could probably be planted 3 feet away and be fine, but not much closer. My blueberry plants that are 2+ feet from my blueberries are currently fine...but my rhubarb plant will assuredly get bigger and therefore closer and compete with their roots more.
So far, my favorite companion plants for blueberries are wood straberries and dandelion (nice taproot and good for pollinators, and edible!). Pansies should work well, if I can just keep my ducks from eating them all. I'm also thinking of adding french sorrel. The french sorrel I've planted elsewhere does spread wide, but not nearly as much as my rhubarb and comfrey, and it's yummy, and it doesn't seem to mind the acidic conditions. My soil is naturally on the acidic side, so I figure if it grows in my soil, it'd probably do well with the blueberries---the only question for me is whether the blueberries would do well with it!
I've also been trying green onions with my blueberries, and would like to add in chives. They're yummy and repel pests. So far, the green onions don't seem to be thriving (maybe they like more alkaline soil?), but I'm hoping the chives will, as chives generally do better on my property than green onions.