How to Grow Watermelon From Seed

Watermelons love heat and cannot tolerate any frost, so timing matters. In warm, long-season regions direct-sow seeds outdoors once the soil is at least 70F and nights stay above 60F, usually 2 to 3 weeks after your last frost. In cooler or short-season climates, start seeds indoors 3 to 4 weeks before your last frost in individual peat or paper pots, then transplant carefully after the soil has warmed. Gardeners in the Deep South and Southwest can plant early enough for a long harvest, while northern growers should lean on early varieties and warmed soil.

Sow seeds about 1 inch deep in warm, rich soil, planting on raised hills or mounds to help the soil warm faster and drain well. Drop 2 to 3 seeds per spot and thin to the strongest seedling, spacing plants 3 to 4 feet apart in rows about 6 feet apart. If starting indoors, use peat or paper pots so you can transplant without disturbing the sensitive roots, and harden plants off over a week before setting them out. Work compost and a handful of balanced fertilizer into each planting hole, and lay down black plastic or dark mulch in cool climates to trap heat.

Watermelons reward steady warmth and generous care. Give them full sun, water deeply and consistently while the vines grow and set fruit, keeping the soil evenly moist, then ease off watering as the melons approach ripeness to concentrate the sugars. Feed with a balanced fertilizer at planting, switch to a lower-nitrogen feed once vines start to run so you get fruit instead of endless leaves, and side-dress again when the melons begin to size up. Mulch to hold moisture and warmth, keep the patch weeded early, and let the sprawling vines run or train compact types up a sturdy trellis with slings to support the fruit.

Watermelons grow well alongside plants that draw in pollinators, lure pests away, or deter beetles and nematodes. Marigolds, nasturtiums, and basil are all classic melon neighbors. These three are especially easy to add in one click:

Watermelons do not ripen further once picked, so harvest at the right moment. Look for the curly tendril nearest the fruit turning brown and dry, the pale ground spot where the melon rests turning creamy yellow, and the rind losing its glossy shine. A ripe melon gives a deep, hollow thump when tapped. Cut the fruit from the vine with a sharp knife or pruners, leaving a short stub of stem, rather than pulling it free.

Few things beat a slice of homegrown watermelon on a hot day. Eat it fresh in wedges, cube it into fruit salads, or blend it into juice, agua fresca, and summer cocktails. Watermelon pairs beautifully with feta, mint, and lime in salads, and even the rind can be pickled. Rich in vitamins A and C and the antioxidant lycopene, it is as refreshing as it is good for you, and a single vine can produce several big melons.

• Poor fruit set: flowers bloom but no melons form, usually from too few pollinators. Plant flowers nearby and hand-pollinate by dabbing pollen from male to female blooms if needed.
• Cucumber beetles: striped or spotted beetles chew leaves and can spread bacterial wilt. Use row covers early (removing them at flowering) and plant nasturtiums as a trap crop.
• Cracked or split fruit: caused by heavy watering after a dry spell. Keep soil moisture even, then reduce water gradually as melons ripen.
• Bland, mealy melons: from cool weather, overwatering late, or picking too early. Give full sun, ease off water near ripening, and wait for the ripeness signs.
• Powdery mildew: white powder on leaves in humid conditions. Space plants for airflow, water at the base, and remove badly affected foliage.