Next time you make a salad, don’t throw away the core you cut from the bottom of your lettuce. Instead, poke a few toothpicks into the bottom to make a little stand, and set the core in a jar. Fill it with water until the bottom of the lettuce is covered by about an inch. After it has sat in a sunny window for a couple of weeks, you’ll see new leaves growing out from the center. You can plant it in the ground or in a pot of soil; harvest the leaves as they grow big enough to eat.