Grandma used to make comfrey ferments in her crock pots that she made her sauerkraut. She grew her own and she always made me harvest it soon after a rain. I guess it was to make sure the plant was cleaner and the bacteria are still intact.I'm busting to get to my local garden centre to pick up a comfrey plant for fermentation. I picked up a pre brewed batch (bo off an organic soil web site In the uk to try out. I added it to my compost tea at the end. Never seen my lady's react so fast to an input. Preying within the hour, I could just tell that there was some special in that furment. Only down side it f-ing stinks bad as it's an anaerobic ferment. But I do think it worth the hassle and smell.
Next time you have a big grow with a heavy defol.....ferment all that!
I've juiced a bunch of defol, gave the juice to the plants and fed the bulk to my worms. Worms LOVE that stuff!