How to grow watermelons: They do not like "wet feet" but they need at least an in of water each wk. You can trellis up watermelon plants, and once the plants set fruit, support the burgeoning melons with slings, which can be made with cheesecloth, nylon stockings, or old T-shirts. If the sling completely covers the fruit, it provides protection from insects. In addition to saving space, trellising improves air circulation and helps prevent disease.