Winters are notoriously harsh in Jackson, Wyoming, where temperatures can plunge far below zero and snowstorms regularly pummel the surrounding mountains. The conditions make for world-class skiing, but they aren’t necessarily conducive to growing heirloom tomatoes. As a result, the majority of vegetables consumed on dinner plates in this remote resort town have to be shipped in through steep canyons or over mountain passes, from locales as far afield as Florida, California, and Mexico. But…