Citron: The Rock-Hard Watermelon Relative Used for Preserves

Citron (Citrullus lanatus var. citroides) is a hard-fleshed, non-sweet watermelon relative. In South Georgia watermelon fields, it's a noxious weed—kids once used the rock-hard fruits to immobilize cars by placing them under tires. The white flesh is candied or used in fruitcakes and preserves. Seeds are available from heirloom suppliers like Rare Seeds. It's a curiosity, not a dessert fruit.