When to Plant Watermelon in Missouri
Published: April 24, 2026
Missouri gardeners in Zone 6b have a 33-week growing season for watermelon (March 22 to November 10). The moderate climate supports a full warm-season crop plus a single main harvest. This guide gives exact dates for Missouri based on your local frost calendar.
Watermelon Planting Dates for Missouri
| Start seeds indoors | March 1–8 |
| Last frost (average) | March 22 |
| Transplant outdoors | April 5–15 |
| Direct sow outdoors | April 5–15 |
| Expect first harvest | June 14 – July 4 |
| First fall frost (average) | November 10 |
Dates above assume Zone 6b, the most common zone in Missouri. Gardeners in cooler St. Louis (Zone 6b) plant 1–2 weeks later; warmer Kansas City (Zone 6a) can plant 1–2 weeks earlier.
⚠ 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 Watermelon in Missouri's Climate
Missouri's moderate Zone 6b climate is well-suited to watermelon with minimal special accommodation. The standard transplant calendar works as written, and harvest windows line up with what seed packets recommend without adjustment.
Succession planting extends your watermelon harvest significantly in Missouri. A second planting 3 to 4 weeks after the first gives you a backup in case of pest pressure and extends the total harvest window into early fall.
Common watermelon pests to watch for in Missouri include Cucumber Beetle and Squash Bug. The first line of defense is companion planting: Corn and Radish planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Watermelon Garden Calendar for Missouri
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
| April | Transplant outdoors | Soil temp must be 65°F+; nighttime lows above 50°F |
| May ← | — | Dormant season |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Continue care | Consistent watering; remove yellow leaves |
| August | — | Dormant season |
| September | — | Dormant season |
| October | — | Dormant season |
| November | First frost approaches | Harvest remaining watermelon; cover plants on frost nights |
| December | — | Dormant season |
Watermelon Growing Tips for Missouri Gardeners
- •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.
- •Missouri's moderate climate supports succession planting — sow new transplants or seeds every 3 weeks during spring to extend the harvest window into fall.
- •Water deeply twice a week during fruit development; reduce watering as melons near ripeness to concentrate sugars.
Companion Planting for Watermelon in Missouri
In Missouri's moderate climate, planting watermelon with Corn and Radish helps deter pests and improve soil. Avoid planting near Cucumber and Potato, which inhibit watermelon growth through root chemistry or shared pest pressure. See the full watermelon companion planting guide for the complete list.
Watermelon Planting Dates by City in Missouri
Top cities in Missouri — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant watermelon in Missouri?
In Missouri (Zone 6b), start watermelon seeds indoors around March 1–8 and transplant outdoors around April 5–15 — 2 weeks after the state's average last frost of March 22.
What is the last frost date in Missouri?
Missouri's average last frost date is March 22 in the state's most common Zone 6b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow watermelon year-round in Missouri?
Not year-round — Missouri's cold season stops watermelon production. The watermelon season runs March 22 to November 10, roughly 33 weeks.
What watermelon varieties grow best in Missouri?
For Missouri's Zone 6b, consult a local nursery or extension office for watermelon variety recommendations.
When do I start watermelon seeds indoors in Missouri?
Start watermelon seeds indoors in Missouri around March 1–8, which is 3 weeks before the state's average last frost of March 22. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.