Well I said I would revive this post so here goes. I've stopped thinking of comfrey and have the medeteranian equivalent acanthus mollis. Along with canna Lilly. The canna Lilly or some other wild Lilly called " platanillo spanish for little banana" is said to be good for corn. The wild stands are cut and then sprayed with weedkiller periodically while the corn is growing.
My method is to just cut cut cut. Un fortunately they don't ocure naturally here so I'm planting my own. I'm not using it for corn because I don't grow that anymore. I use it around trees and other plants tall
enough not to get killed by mulch. It spreads slowly so it can be maintained in rows or clumps between crop rows or beds. I like working in circles, no pun intended lol, you could have a platanillo patch at center with some chayotes in it. Around that some trees and Napier grass. I mulch the smaller weeds out and leave the canna patch unmulched for regrowth. Sometimes I dice the canna trunks so they don't get in the way if I try to weed later
Acanthus m could possibly harm your plants if used as mulch so be careful. That said, its herbicide affect may kill more weeds. And it's soft so no choping up. Another plus is that it's not very tall so big plants can't be shaded out by it, canna is tall up to 9 feet. Acanthus will crowd your plants out if you don't cut it often.