Did you know you can eat radish leaves? I just learned this from the informative Chocolate and Zucchini blog entry on this subject.
I've tried it, so I can say that the leaves are, er, bitter, not to mention a bit prickly, but they certainly are edible.
The pesto is earthy, not quite like the basil-based pesto you might think of. But the texture is the same and if you put it on your very favorite crackers, you'll probably like it as much as I do. Chew, swallow, smile, and think, I'm eating healthy and free food! I mean, what would you do with those leaves otherwise?
Clotilde also suggests putting the leaves in casseroles and soups where the strong flavor of the radish leaves won't upset any delicacy of the dish.