When to plant watermelons in New Jersey
New Jersey’s average last spring frost is April 20, and the first fall frost typically arrives around October 15 — about 178 frost-free days (USDA zones 6a, 6b, 7a, 7b). Watermelon needs 70–100 days to mature, which fits comfortably within New Jersey's growing season.
When to plant watermelons in New Jersey: the short answer
For a spring planting, plant out Apr 27 – May 14, with seeds started indoors Mar 23 – Apr 6. 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 New Jersey, step by step
- Start seeds indoors (Mar 23 – Apr 6). 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 27 – May 14). 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 13 – Aug 12). 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 New Jersey’s average frost dates. More in the full watermelon growing guide.
Watermelon planting dates by USDA zone in New Jersey
New Jersey spans USDA zones 6a, 6b, 7a, 7b. 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 |
|---|---|---|
| New Jersey (this page) | April 20 | Apr 27 – May 14 |
| Pennsylvania | May 1 | May 8 – May 25 |
| Delaware | April 14 | Apr 21 – May 8 |
| 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 New Jersey ask
When is the best time to plant watermelons in New Jersey?
Plant watermelon transplants outdoors in New Jersey between April 27 and May 14. That timing is set by New Jersey's average last spring frost of April 20.
When should I start watermelon seeds indoors in New Jersey?
Start seeds indoors between March 23 and April 6, about 3 weeks before the last frost, so the seedlings are ready to plant out from April 27.
What is the latest I can plant watermelons in New Jersey?
About August 6. Watermelons need at least 70 days to mature, and frost around October 15 ends the season, so later plantings risk being cut short.
When will watermelons planted in New Jersey be ready to harvest?
Planted on time, watermelons are usually ready from about July 13 to August 12, 70-100 days after planting.
When is the last frost in New Jersey?
On average around April 20, with the first fall frost around October 15 - about 178 frost-free days. Your town may differ by two weeks or more.