How to grow watermelon

Citrullus lanatus · Cucurbitaceae · Fruit

Watermelon is a warm-season fruiting crop in the Cucurbitaceae family, grown either from a direct sowing or from transplants. It wants full sun (six or more hours of direct light) and steady, even moisture. From sowing to first pick is about 70–100 days. It is killed by frost, so nothing goes outside until the danger has passed and the soil has warmed.

Grower’s note: Longest-season cucurbit here - icebox varieties (70-75 days) are the realistic choice north of the mid-Atlantic. Ripe when the curly tendril nearest the fruit is brown and dry and the ground spot is buttery yellow.

Sowing

Sow about 1″ deep, into soil between 70–95°F — germination is quickest near 85°F. It comes up fast (4–10 days). For an early crop, start seed indoors about 3 weeks before your last spring frost and grow it under bright light.

Spacing & layout

Give each plant about 36″ along the row with roughly 72″ between rows. On a square-foot grid that is one plant per 4 square feet. Allow at least 24″ of loose, workable soil for the roots. It needs more root room than most containers give and does best in the ground.

Fitting it to your season

Watermelon needs roughly 70–100 frost-free days to crop. Where the season is shorter than that, start it indoors and choose the earliest-maturing varieties, or grow it in a container you can move under cover on cold nights. In long, hot-summer regions it can often be planted twice — once in spring and again in mid-to-late summer for a fall harvest.

Quick facts

When to plant watermelon

Companions

Common problems

Pests: striped cucumber beetle, aphids, squash vine borer.

Diseases & disorders: anthracnose, fusarium wilt, powdery mildew, gummy stem blight.

Same family (Cucurbitaceae)

Rotate these so they don’t follow each other in the same bed year to year.

Figures are typical home-garden ranges from Cooperative Extension planting guides, cross-checked against multiple state sources. Your variety and conditions will vary.