I understand that there are contests around the world to see who can eat the most raw nettle leaves without vomiting, despite the sting. I've never tried it (and probably never will), but supposedly you can roll a fresh leaf upside-down, from base to edge, and eat it raw without getting stung. I think I'll skip. Nettles are too good cooked to bother. Creamed nettles, nettle pesto, nettle dip, nettle green sauce, nettle fak'a hoy - the last two are African recipes worth dying for. It's probably unfair of me not to print the recipes here. Sorry, I can't give away all my secrets.
The flavor of Knotweed isn't like asparagus. It actually has a flavor. It's just a little tart, and the texture has a little crunch to it. It's good enough prepared simply, sauteed in butter or oil with salt and pepper, that you may never try it any other way. It's the young shoots - eight inches tall or less - that you eat this way. Older, taller shoots can be peeled and sliced and used like rhubarb. Don't confuse it with Poke, another Spring shoot which grows under last year's stalks; Poke needs to be cooked in two changes of water.
Once you start eating wild foods, you'll be amazed at how many there are around, and how prolifically they grow. They are there for the taking. Spring is here, and it's time to eat some weeds!