When to plant watermelons in Missouri
Missouri’s average last spring frost is April 15, and the first fall frost typically arrives around October 18 — about 186 frost-free days (USDA zones 5b, 6a, 6b, 7a). Watermelon needs 70–100 days to mature, which fits comfortably within Missouri's growing season.
When to plant watermelons in Missouri: the short answer
For a spring planting, plant out Apr 22 – May 9, with seeds started indoors Mar 18 – Apr 1. Wait until the soil is at least 70°F and frost is over.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow watermelons in Missouri, step by step
- Start seeds indoors (Mar 18 – Apr 1). Sow seeds 1 inch deep in seed-starting mix under bright light. They take 4-10 days to sprout, fastest in soil around 85°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. They need at least six to eight hours of direct sun a day and loose soil at least 24 inches deep, with a pH between 5.5 and 6.8. Dig in compost before planting.
- Plant out (Apr 22 – May 9). Space plants about 36 inches apart in rows 72 inches apart. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: striped cucumber beetle, aphids, squash vine borer. Diseases and disorders: anthracnose, fusarium wilt, powdery mildew, gummy stem blight.
- Harvest (from about Jul 8 – Aug 7). Watermelon takes 70-100 days to reach harvest. 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.
Figures come from our crop data; dates use Missouri’s average frost dates. More in the full watermelon growing guide.
Watermelon planting dates by USDA zone in Missouri
Missouri spans USDA zones 5b, 6a, 6b, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the watermelon dates shift with them.
When to plant watermelons in nearby states
Questions gardeners in Missouri ask
When is the best time to plant watermelons in Missouri?
Plant watermelon transplants outdoors in Missouri between April 22 and May 9. That timing is set by Missouri's average last spring frost of April 15.
When should I start watermelon seeds indoors in Missouri?
Start seeds indoors between March 18 and April 1, about 3 weeks before the last frost, so the seedlings are ready to plant out from April 22.
What is the latest I can plant watermelons in Missouri?
About August 9. Watermelons need at least 70 days to mature, and frost around October 18 ends the season, so later plantings risk being cut short.
When will watermelons planted in Missouri be ready to harvest?
Planted on time, watermelons are usually ready from about July 8 to August 7, 70-100 days after planting.
When is the last frost in Missouri?
On average around April 15, with the first fall frost around October 18 - about 186 frost-free days. Your town may differ by two weeks or more.