To my right is Mexico, separated by only a few fields of lettuce. "Buenos días," Manuel says. I stand up gingerly. It's only my third day in the fields, but already my 30-year-old body is failing me.

Bagged lettuce is one of the most convenient, easy-to-use healthy ingredients at the grocery store, so why must it also be one of those that goes bad the fastest? Indeed, it seems like bagged salad ...