Sweet, juicy homegrown watermelons capture the magic of summer with explosive taste that puts store-bought melons to shame. Like their cantaloupe cousins, watermelons demand 2 to 3 months of heat to produce ripe fruit, which makes growing watermelons in northern regions challenging, but not impossible. By using plastic mulch to warm soil and floating row covers to trap warm air near plants, gardeners in any part of the country can experience the homegrown goodness of watermelons.