I have an endless supply of coffee grounds, but have been finding that they are too nitrogen rich for many of my fruiting plants (container garden). I've been thinking lately of growing comfrey directly in used coffee grounds (or something like 75% coffee grounds, 25% soil) to create lots of comfrey biomass and then make comfrey tea for my plants. I figure I can put composting worms in there too so that I get worm castings as well.
Anyone have thoughts on whether this will work, or other alternative approaches to processing the coffee grounds easily to get a more balanced amendment out of them? (I've considered doing a worm bin with them, but I'd like other alternatives as well.)
Hmm, seems like too much coffee grounds to me. I might try it if I was doing potatoes or sunchokes, not sure how comfrey will fair. Honestly I would use those coffee grounds to get yourself some oysters or wine caps, then feed to the worms for nice compost and get some function stacking as well.
It sounds like a good experiment to do, Bob, and if you can handle the stench of comfrey tea you're a better man than I am. Some plants given an excess of nitrogen become toxic to livestock, and the comfrey tea may still be too rich for your other plants.
But while you're doing your experiment with part of the grounds, why not cut the rest with some brown matter and put them to work right away? Wood chips are usually easy and free to obtain...