Watermelons (Citrullus lanatus) are summertime fruits, and with so many varieties to choose from, there's a type for almost any size garden. Its juicy, sweet flesh is usually eaten fresh, but is also used in pureed smoothies, frozen granitas and other desserts. Purchase healthy watermelon transplants from reputable garden centers or start from seed.
Watermelons are annual plants with long trailing stems. Its stems are thin, angular, hairy and grooved, with branched tendrils. Watermelon root systems grow deeply into the soil compared with some other members of the cucurbit family, but still relatively shallow. Its leaves are deeply lobed. Small and solitary, pale yellow flowers are insect pollinated, and open for one day. Fruit size, sugar content, shape and surface and interior color vary widely among cultivars. Seedless varieties need to be grown with seeded (pollinator) varieties to produce melons.
Watermelons prefer 70 to 80 degrees F daytime temperatures and 65 to 70 degrees F nights. Grow in rich, organic soil in hills of two or three plants, or according to seed packet or transplant instructions. Spacing depends on which cultivar is grown--whether it's a small bush-type, small vine melon (5 to 8 lbs.) or large vine melon (more than 15 lbs.). Use of black plastic mulch conserves soil moisture, suppresses weed growth and warms the soil in cool climates. Fertilize watermelons with 10-10-10 fertilizer or fish emulsion if the leaves turn yellow. Keep the soil evenly moist until fruit sets and then when the top 1 inch of soil becomes dry.
Harvest and Storage
Harvest watermelons when the nearest tendril to the fruit stem is brown and the bottom of the fruit where it rests on the ground has turned yellow. Thumping a ripe watermelon will result in a dull, muffled sound, unlike thumping an immature fruit which will result in a clear tone. Store uncut watermelons at room temperature until ready to chill and eat. Store tightly covered cut watermelon in the refrigerator for two to three days.
Pick the right size watermelon for your needs. Varieties include early season (70 to 75 days to harvest), main season (80 to 85 days to harvest) and seedless (80 to 85 days to harvest). Some small early types are 'Golden Crown,' 'Sugar Baby,' 'Yellow Baby' and 'Yellow Doll.' Large, main season types include 'Charleston Gray,' 'Crimson Sweet' and 'Sweet Favorite.' Seedless watermelons include 'Cotton Candy,' weighing 15 to 20 lbs., 'Honey Heart,' weighing 8 to 10 lbs. and 'Tiffany,' weighing 14 to 22 lbs.
Choose disease-resistant watermelon varieties to reduce diseases such as fusarium and verticillium wilt. Control disease-spreading insects, such as aphids and cucumber beetles, with a horticultural insecticide or use ladybugs for the aphids and kill cucumber beetles when you observe them in the garden. Your local county extension office is a recommended source of information regarding disease and pest identification and management.