I have had Fagopyrum cymosum (perennial buckwheat) in my food forest for two years. It grew prolifically on the sun side of a raspberry patch, an apple tree and a silk tree in spite of being decimated by snails in the spring. I had one plant last year, which became 30+ stalks this year. Raw it is quite bitter (towards a dandelion taste), cooked it is wonderful. I made a palak paneer with it that tastes exactly like the version I make with spinach. I have been harvesting by cutting off the stalks to keep the growth down. I haven't tried harvesting seeds yet. The stalks are hollow, so I think they will make good insect hideouts if I leave them lying around in the fall. It seems like a perfect permaculture plant! My food forest is in Germany and I ordered my first plant from
https://www.kraeuter-und-duftpflanzen.de. As far as I know, they only deliver within Europe.