Watermelons need heat, space and time, but a ripe one from your own garden is the taste of summer. They are warm-season vines that want full sun, warm sandy soil and plenty of water while fruit grows. Small icebox varieties fit smaller gardens and shorter seasons. This page covers when to sow, how much room to give, how to water and feed, and how to tell when a watermelon is ripe.
Watermelon at a glance
| Type | Fruit |
|---|---|
| Season | Warm-season |
| Sun | Full sun |
| Plant spacing | 48 in |
| Row spacing | 72 in |
| Per square foot | 1 per 9 sq ft |
| Seed depth | 1 in |
| Days to maturity | 80–100 from seed |
| How to start | Direct sow 1–2 weeks after last frost in warm soil, or indoors 3–4 weeks before |
| Water | 1.5 in per week |
These are the same numbers our plant spacing, square foot and harvest date calculators use. See every crop in the plant database.
When to plant watermelon
Watermelon seeds need warm soil, about 70°F, to germinate well. Sow directly outdoors 1 to 2 weeks after your last spring frost. In short-season areas, start seeds indoors in individual pots 3 to 4 weeks before the last frost and transplant carefully, because watermelons dislike root disturbance.
Check your last frost with the frost dates by ZIP code tool, and check your frost-free days with the growing season length calculator; most varieties need 80 to 100 warm days.
How to plant watermelon
- Choose full sun and sandy, well-drained soil. Work in compost. In cool areas, warm the soil with black plastic before planting.
- Sow 2 or 3 seeds per spot. Plant 1 inch deep and thin to the strongest seedling.
- Plan for big vines. Vines can run 10 to 20 feet. Use the spacing in the table above, and the plant spacing calculator to see how many fit. Small icebox types can be trellised with fruit slings.
- Use row cover early. It warms young plants and keeps beetles off. Remove it when flowers open.
Caring for watermelon
Give 1 to 2 inches of water a week from planting through fruit set and growth, watering at the base. Once fruits reach full size, reduce watering for the last week or two to concentrate sweetness and prevent splitting. The garden watering calculator turns this into gallons.
Side-dress with compost or a balanced fertilizer when vines start to run, then switch to a lower-nitrogen feed at flowering. Rest developing fruit on straw or a board to keep it dry. Limit large varieties to 2 or 3 fruits per vine for bigger melons.
Companion plants
| Grow nearby | Nasturtiums, marigolds, radishes, corn, sunflowers |
|---|---|
| Keep apart | Potatoes; cucumbers and squash right beside them share pests and disease |
Nasturtiums and radishes are said to deter beetles, and flowers bring in bees for pollination. Melons can run between rows of corn. Check other pairings with the companion plant finder.
Common problems
| Problem | What you see | What to do |
|---|---|---|
| Fusarium wilt | Vines wilt and yellow, often one runner at a time | No cure. Grow resistant varieties and rotate melons to a new spot for several years. |
| Cucumber beetles | Yellow beetles with stripes or spots chewing leaves | Use row cover until flowering and hand-pick. See the pest identifier. |
| Anthracnose | Dark, sunken spots on fruit and brown spots on leaves | Remove affected leaves, water at the base and rotate crops. |
| Blossom-end rot | Dark, leathery patch at the end of the fruit | Water evenly and mulch. |
| Small or misshapen fruit | Lopsided or undersized melons | Poor pollination or uneven water. Plant flowers for bees and keep moisture steady. |
Not sure what you are looking at? The plant problem identifier ranks likely causes from the symptoms you see.
When and how to harvest
Watermelon ripeness takes a few clues together. The curly tendril nearest the fruit turns brown and dry. The spot where the melon rests on the ground turns from white to creamy yellow. The rind loses its shine and turns dull, and a ripe melon gives a deep, hollow sound when thumped, while an unripe one sounds higher.
Cut the melon from the vine with a knife or pruners. Watermelons do not ripen further after picking, so wait for the signs. Whole melons keep for 1 to 2 weeks at cool room temperature; refrigerate once cut. Use the harvest date calculator to estimate when to start checking.
Plan your watermelon
- Plant spacing calculator: how many plants fit your bed
- Planting calendar: sowing and transplant dates for your frost dates
- Frost dates by ZIP code: your last spring and first fall frost
- Harvest date calculator: when your crop will be ready
Frequently asked questions
How far apart should I plant watermelons?
Space watermelons 48 inches apart in rows 72 inches apart. In a square foot garden, plant 1 per 9 sq ft.
How deep do I plant watermelon seeds?
Sow seeds 1 inch deep. Sow 2 or 3 seeds per spot and thin to the strongest seedling.
How long do watermelons take to grow?
Most varieties are ready 80–100 days from seed. Check the seed packet, because early and late varieties differ.
How much water do watermelons need?
About 1.5 inches of water a week, from rain and watering combined. Reduce watering for the last week or two before harvest.
How do I know when a watermelon is ripe?
The tendril nearest the fruit dries and turns brown, the ground spot turns creamy yellow, the rind turns dull and the melon sounds deep and hollow when thumped.
How many watermelons grow on one plant?
Large varieties usually ripen 2 to 3 fruits per vine; small icebox types can give a few more.