When to plant watermelons in Indiana
Indiana’s average last spring frost is April 24, and the first fall frost typically arrives around October 11 — about 170 frost-free days (USDA zones 5b, 6a, 6b). Watermelon needs 70–100 days to mature, which fits comfortably within Indiana's growing season.
When to plant watermelons in Indiana: the short answer
For a spring planting, plant out May 1 – May 18, with seeds started indoors Mar 27 – Apr 10. 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 Indiana, step by step
- Start seeds indoors (Mar 27 – Apr 10). 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 (May 1 – May 18). 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 17 – Aug 16). 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 Indiana’s average frost dates. More in the full watermelon growing guide.
Watermelon planting dates by USDA zone in Indiana
Indiana spans USDA zones 5b, 6a, 6b. 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 Indiana ask
When is the best time to plant watermelons in Indiana?
Plant watermelon transplants outdoors in Indiana between May 1 and May 18. That timing is set by Indiana's average last spring frost of April 24.
When should I start watermelon seeds indoors in Indiana?
Start seeds indoors between March 27 and April 10, about 3 weeks before the last frost, so the seedlings are ready to plant out from May 1.
What is the latest I can plant watermelons in Indiana?
About August 2. Watermelons need at least 70 days to mature, and frost around October 11 ends the season, so later plantings risk being cut short.
When will watermelons planted in Indiana be ready to harvest?
Planted on time, watermelons are usually ready from about July 17 to August 16, 70-100 days after planting.
When is the last frost in Indiana?
On average around April 24, with the first fall frost around October 11 - about 170 frost-free days. Your town may differ by two weeks or more.