When to plant watermelons in Delaware
Delaware’s average last spring frost is April 14, and the first fall frost typically arrives around October 22 — about 191 frost-free days (USDA zones 7a, 7b). Watermelon needs 70–100 days to mature, which fits comfortably within Delaware's growing season.
When to plant watermelons in Delaware: the short answer
For a spring planting, plant out Apr 21 – May 8, with seeds started indoors Mar 17 – Mar 31. 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 Delaware, step by step
- Start seeds indoors (Mar 17 – Mar 31). 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 21 – May 8). 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 7 – Aug 6). 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 Delaware’s average frost dates. More in the full watermelon growing guide.
When to plant watermelons in nearby states
| State | Last frost | Plant out |
|---|---|---|
| Delaware (this page) | April 14 | Apr 21 – May 8 |
| New Jersey | April 20 | Apr 27 – May 14 |
| Pennsylvania | May 1 | May 8 – May 25 |
| Maryland | April 14 | Apr 21 – May 8 |
| District of Columbia | April 10 | Apr 17 – May 4 |
| Virginia | April 15 | Apr 22 – May 9 |
| West Virginia | May 5 | May 12 – May 29 |
Questions gardeners in Delaware ask
When is the best time to plant watermelons in Delaware?
Plant watermelon transplants outdoors in Delaware between April 21 and May 8. That timing is set by Delaware's average last spring frost of April 14.
When should I start watermelon seeds indoors in Delaware?
Start seeds indoors between March 17 and March 31, about 3 weeks before the last frost, so the seedlings are ready to plant out from April 21.
What is the latest I can plant watermelons in Delaware?
About August 13. Watermelons need at least 70 days to mature, and frost around October 22 ends the season, so later plantings risk being cut short.
When will watermelons planted in Delaware be ready to harvest?
Planted on time, watermelons are usually ready from about July 7 to August 6, 70-100 days after planting.
When is the last frost in Delaware?
On average around April 14, with the first fall frost around October 22 - about 191 frost-free days. Your town may differ by two weeks or more.