Watermelon
Also known as
Common watermelon, Watermelon vine, Egusi melon (seed type)
Keep this plant’s care guide close at hand.
Get the appAbout Watermelon
Citrullus lanatus is a warm-season, sprawling annual vine in the cucurbit family grown primarily for its large, juicy fruits. Originating in Africa, it produces long, ridged vines with deeply lobed leaves, tendrils, and separate male and female flowers that rely on pollinators, especially bees. Fruits range from small icebox types to large picnic melons, with rinds that may be striped or solid and flesh colors spanning red, pink, yellow, and orange. Watermelon thrives in hot, sunny conditions, requiring well-drained, fertile soil and ample space for vines to ramble. It is a heavy feeder and a consistent drinker during vegetative growth and fruit set, yet benefits from reduced moisture as fruits finish ripening to concentrate sugars. Cultivation challenges include damping-off in cool soils, blossom-end issues from uneven moisture, and pests such as cucumber beetles, aphids, and squash bugs. Harvest timing is gauged by a dried tendril near the fruit, a creamy ground spot, and a resonant thump.
Taxonomy
Properties & Requirements
How to care for Watermelon
Water
Provide deep, consistent moisture—about 1–1.5 inches (25–38 mm) of water per week—especially from vining through fruit set. Drip irrigation or soaker hoses are ideal to keep foliage dry and reduce disease. Water early in the day and mulch to maintain even soil moisture. Avoid prolonged droughts followed by heavy soaking, which can cause fruit splitting. As harvest nears, modestly taper irrigation to enhance sweetness, but don’t allow plants to wilt or suffer severe stress.
Light
Provide full sun—at least 8 hours daily (6 hours minimum), with 10+ hours ideal for high sugars and full yield. Watermelon needs high light intensity; in greenhouses target a daily light integral around 20–30 mol·m⁻²·day⁻¹. Avoid shade from taller crops or structures. In extreme heat, a light 15–20% shade cloth can reduce flower stress without compromising fruit quality. Indoor windowsill culture is unsuitable; use outdoor beds or high-light greenhouse conditions.
Nutrients
Incorporate well-aged compost or manure before planting and use a balanced starter (e.g., 10-10-10) at transplant or vining. Side-dress nitrogen (e.g., calcium nitrate) when vines start running and again just before flowering, then reduce nitrogen after fruit set to favor sugars. Maintain adequate potassium and phosphorus based on a soil test; avoid chloride-heavy K sources on saline soils. Apply micronutrients only if deficient. Keep soil pH near 6.0–6.8 and mulch to conserve nutrients and moisture.
Temperature
Watermelon is strictly warm-season. Germination is best at 75–90°F (24–32°C) and growth is optimal at 70–90°F (21–32°C). Transplant only after danger of frost when soil is consistently above 70°F (21°C). Chilling injury occurs below ~50°F (10°C), and prolonged heat above ~95°F (35°C) with hot nights can reduce fruit set. In marginal climates, use black plastic mulch or low tunnels to warm soil, removing covers at flowering to allow pollinators access.
