When to Plant Watermelon
Published: April 24, 2026
Heat-loving vining crop that needs 70–90 frost-free days and consistently warm soil. Direct sow in warm climates; start indoors in Zones 4–5 to squeeze in a harvest before fall.
When to plant watermelon
- Start seeds indoors: 3 weeks before last frost
- Direct sow outdoors: 2 weeks after last frost
- Minimum soil temperature: 65°F
- Days to harvest: 70–90 days
- Sun requirement: Full sun (8+ hours)
- Spacing: 48 inches apart
- Water: 2 inches per week
- Fall crop: No — single spring/summer crop only
⚠ Plant watermelon 2 weeks after last frost when soil exceeds 65°F. Needs 70–90 frost-free days. Direct sow in warm climates; start indoors in Zone 4–5.
Growing Tips for Watermelon
- •Plant on a warm, sunny slope or use black plastic mulch to maintain soil temperature above 70°F all season.
- •Give each plant 6 feet of space — watermelon vines sprawl and need room to run.
- •Water deeply twice a week during fruit development; reduce watering as melons near ripeness to concentrate sugars.
- •Test ripeness by thumping (hollow sound), checking the curly tendril nearest the fruit (should be brown), and the ground spot (should be creamy yellow).
Companion Planting for Watermelon
✅ Plant watermelon with
- • Corn
- • Radish
- • Nasturtium
- • Marigold
❌ Avoid planting near
- • Cucumber
- • Potato
- • Fennel
Common Watermelon Pests and Problems
Regional pest pressure varies — see your state guide below for state-specific pest calendars and treatment timing.
Watermelon Planting Dates by State
Select your state for exact sow and transplant dates based on local frost calendars.
Frequently Asked Questions
When do I plant watermelon?
Plant watermelon 2 weeks after your last frost date, once soil temperature is consistently above 65°F. In Zones 3–5 this is early June; in Zones 7–9 it is mid-May. Cold soil causes seeds to rot and stunts transplants — warm soil matters more than the frost calendar for this crop.
Should I start watermelon seeds indoors?
In Zones 3–5, start watermelon seeds indoors 3 weeks before transplanting (about 5 weeks before last frost) in large peat pots. Watermelons dislike root disturbance. In Zones 6+, direct sowing produces equally good results and avoids transplant shock. Wait for soil to reach 65°F either way.
How do I know when a watermelon is ripe?
Three ripeness indicators: the curly tendril nearest the fruit turns brown and dry, the ground spot where the melon rests turns from white to creamy yellow, and the rind loses its glossy shine for a dull finish. A hollow sound when thumped confirms ripeness. Once picked, watermelons do not continue ripening.
Can I grow watermelon in a short-season climate?
Yes, with short-season varieties like Sugar Baby (75 days) or Blacktail Mountain (73 days). Pre-warm soil with black plastic mulch 2 weeks before planting. Use row covers until flowering to create a warmer microclimate. Zone 3 is marginal — start indoors and plant the earliest possible warm soil date.
What should I plant with watermelon?
Corn provides light shade in peak summer heat. Radishes deter cucumber beetles. Nasturtiums and marigolds repel squash bugs. Avoid cucumbers (cross-pollinate and share pests), potatoes (compete for nutrients), and fennel (allelopathic).