Japanese knotweed shoots are similar in appearance and speed of growth to asparagus, but in flavor they're very similar to rhubarb. Pick nice fat shoots when they're a foot tall or less, strip off any leaves, and use it as you would rhubarb. Today I'm making a knotweed crumble. Knotweed shoots are hollow, so use a bit more per recipe than you would rhubarb since it shrinks down more as it cooks. It's also slightly less tart than rhubarb, so I like to add a little lemon juice. I first learned about eating knotweed from "Wildman" Steve Brill's website, which includes lots of recipes and great information about the plant (along with lots of other great foraging advice).
So, do your civic duty and harvest some knotweed shoots, and get a free meal in the bargain!