It is a truth universally acknowledged that, if one is in possession of some kind of green thing and some kind of nut, one can make some kind of pesto. Frothy carrot tops? Whiz them in the food processor with almonds. Transform your broccoli or your thyme windfall. Use up a bag of arugula on its last legs by blending it up with walnuts and olive oil and Parmesan. What you do with it then? It's up to you—but pasta (or toast, or eggs, or salad) is always a safe bet.
Here are 19 of our favorite pestos—from the classic (basil) to the funkier (chard stems):