Amy Stewart had a simple dream. She yearned for a garden filled with colorful jumbles of vegetables and flowers. After she and her husband finished graduate school, they pulled up their Texas roots and headed west to Santa Cruz, California. With little money in their pockets, they rented a modest seaside bungalow with a small backyard. It wasn't much--a twelve-hundred-square-foot patch of land with a couple of fruit trees, and a lot of dirt. A good...