When to plant watermelons in Oklahoma
Oklahoma’s average last spring frost is April 1, and the first fall frost typically arrives around November 1 — about 214 frost-free days (USDA zones 6b, 7a, 7b, 8a). Watermelon needs 70–100 days to mature, which fits comfortably within Oklahoma's growing season.
When to plant watermelons in Oklahoma: the short answer
For a spring planting, plant out Apr 8 – Apr 25, with seeds started indoors Mar 4 – Mar 18. 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 Oklahoma, step by step
- Start seeds indoors (Mar 4 – Mar 18). 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 8 – Apr 25). 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 Jun 24 – Jul 24). 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 Oklahoma’s average frost dates. More in the full watermelon growing guide.
Watermelon planting dates by USDA zone in Oklahoma
Oklahoma spans USDA zones 6b, 7a, 7b, 8a. 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
| State | Last frost | Plant out |
|---|---|---|
| Oklahoma (this page) | April 1 | Apr 8 – Apr 25 |
| North Dakota | May 15 | May 22 – Jun 8 |
| South Dakota | May 10 | May 17 – Jun 3 |
| Nebraska | April 30 | May 7 – May 24 |
| Kansas | April 15 | Apr 22 – May 9 |
Questions gardeners in Oklahoma ask
When is the best time to plant watermelons in Oklahoma?
Plant watermelon transplants outdoors in Oklahoma between April 8 and April 25. That timing is set by Oklahoma's average last spring frost of April 1.
When should I start watermelon seeds indoors in Oklahoma?
Start seeds indoors between March 4 and March 18, about 3 weeks before the last frost, so the seedlings are ready to plant out from April 8.
What is the latest I can plant watermelons in Oklahoma?
About August 23. Watermelons need at least 70 days to mature, and frost around November 1 ends the season, so later plantings risk being cut short.
When will watermelons planted in Oklahoma be ready to harvest?
Planted on time, watermelons are usually ready from about June 24 to July 24, 70-100 days after planting.
When is the last frost in Oklahoma?
On average around April 1, with the first fall frost around November 1 - about 214 frost-free days. Your town may differ by two weeks or more.