Watermelons originated in Africa, but over the centuries they’ve become part of the American vernacular, ingrained in our culture and traditions. Heirloom watermelons have long been valued by farmers and gardeners, who saved seed year after year for replanting. Humans and watermelons have become “evolutionarily linked.” They exist to feed the people who treasure them. I’m a fan of traditional seeded watermelons of all sizes, shapes, and rind patterns. The giant ones have a special place in my heart.
Heirloom (seeded and open-pollinated) varieties are still grown and relished, but the number is dwindling. Seedless sorts dominate the marketplace. Many consumers prefer small seedless watermelons because they’re “easy,” not realizing that if seeded varieties disappear, something precious will be irretrievably lost.
Mark Twain praised southern-grown watermelons as “a boon apart,” king of all fruits, fit for angels. That the flavor of watermelons grown in the South is unsurpassed is true. Watermelons thrive and reach their fullest expression in long-season areas with hot, dry, sunny weather. With days in the 80s and nights in the 60s, plants yield luscious fruit in as little as 3 months. But you don’t need a southern ZIP code to grow tasty watermelons. There are ways to stretch the season with row covers, hot caps, and plastic mulch.
The best place for growing watermelons is a site in full sun—with a windbreak, so trailing vines don’t flap in the breeze. If you have deep and well-drained soil, such as sandy loam, consider yourself lucky. Watermelons fare poorly in waterlogged and compacted soils. Adding soil amendments and organic matter helps and can provide essential plant nutrients. Aim for an acidic soil, with a pH between 6.0 and 6.5.
For a bumper crop of watermelons, I recommend laying down black plastic mulch. Unsustainable as it may be, in this case plastic is useful: It heats the soil, producing earlier and more abundant harvests. Wide spacing is also key to bigger harvests—and bigger fruits. I cut holes in the plastic 2 feet in diameter, at 12-to-15-foot intervals, and place several plants in each opening. I keep them under spun-polyester row covers for several weeks to protect against the elements, removing the covers once plants begin to sprawl and then flower, setting fruit with the aid of bees.
Primary prevention is how I deal with the pests and diseases that attack watermelons. It includes vigilance, disposal of crop debris, rotation, mulches, wide spacing, those spun-polyester covers, and judicious watering. The most likely animal pests to look out for early in the season are rodents that unearth seeds or young plants. Defend ripening fruits from hungry deer, raccoons, and crows with fencing, trapping, and scarecrows. Root-knot nematodes (roundworms that inhabit the soil) produce root galls on infected plants; stunting, yellowing leaves, wilting, and poor yields follow. Both nematodes and fusarium wilt—a disease produced by soil fungus that causes wilt, yellowing of leaves, and lesions or cracking on vines—can be prevented with crop rotation and good field sanitation.
The earliest watermelons will start ripening about 3 months after transplanting. It’s time to pick when the “ground spot” on the underbelly becomes yellow, or the tendril nearest the stem withers, and the melon acquires a weighty feel and a dull rind.
Harvested watermelons should be stored at 55° to 60°F and are best eaten within 3 weeks postharvest. When the fruit is ripe and ready, so are the seeds. If you save and share your seeds with others for replanting, you’ll do your part to keep a rich heritage alive.
Six Heirloom Watermelons Worth Growing
‘Blacktail Mountain’. Small (12 to 18 pounds) and round with dark green rind; dense scarlet flesh is very sweet, juicy, and crunchy. Bred for early maturity and cold tolerance, but widely adapted.
‘Golden Midget’. An oval miniature watermelon (averages 3 to 5 pounds) with a penciled yellow rind and salmon-pink flesh. Resembles papaya; tastes as good as it looks. Early variety with a compact habit.
‘Moon and Stars’ (yellow-fleshed). A cosmic melon. Foliage and fruits are speckled with yellow markings resembling moons and stars. Medium-sized (18 to 24 pounds). Sweet, orangey-yellow flesh. Totally wonderful. Late maturity.
‘Orangeglo’. Sugary firm-fleshed melon with orange flesh. Large (24 to 32 pounds) elongated fruits with dark green stripes. Very vigorous and productive main crop variety.
‘Petite Yellow’. A yellow-fleshed seeded watermelon. Small round icebox size (averages 5 pounds) has high sugars and holds together better than other yellow sorts. Matures early; suitable for short-season areas.
‘Sweet Siberian’. A melon with origins in Russia. Blocky dark green icebox type (averages 10 pounds) with apricot-colored flesh and light brown seeds. Sweet, crunchy; somewhat fibrous.