When to plant sweet corn in New Hampshire
New Hampshire’s average last spring frost is May 13, and the first fall frost typically arrives around September 25 — about 135 frost-free days (USDA zones 3b, 4a, 4b, 5a, 5b, 6a). Sweet Corn needs 60–100 days to mature, which fits comfortably within New Hampshire's growing season.
When to plant sweet corn in New Hampshire: the short answer
For a spring planting, sow May 15 – Jun 3. Wait until the soil is at least 55°F and frost is over.
Succession sow again in New Hampshire: Jun 3 · Jun 17 · Jul 1
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 sweet corn in New Hampshire, step by step
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 24 inches deep, with a pH between 5.8 and 7.0. Dig in compost before planting.
- Sow outdoors (May 15 – Jun 3). Space plants about 10 inches apart in rows 30 inches apart, sowing seed 1.5 inches deep. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. It needs plenty of water; keep the soil evenly moist and never let it dry out.
- Watch for pests and problems. Pests: corn earworm, European corn borer, corn rootworm, raccoons. Diseases and disorders: common smut, common rust, Stewart's wilt.
- Harvest (from about Jul 19 – Aug 28). Sweet Corn takes 60-100 days to reach harvest. Plant in a block of at least 4 short rows, not one long row, or the ears fill unevenly. Keep sugar-enhanced and supersweet types isolated from field corn. Succeed by sowing every 2 weeks or planting early/mid/late varieties together.
Figures come from our crop data; dates use New Hampshire’s average frost dates. More in the full sweet corn growing guide.
Sweet Corn planting dates by USDA zone in New Hampshire
New Hampshire spans USDA zones 3b, 4a, 4b, 5a, 5b, 6a. 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 sweet corn dates shift with them.
When to plant sweet corn in nearby states
| State | Last frost | Sow |
|---|---|---|
| New Hampshire (this page) | May 13 | May 15 – Jun 3 |
| Maine | May 14 | May 16 – Jun 4 |
| Vermont | May 14 | May 16 – Jun 4 |
| Massachusetts | April 24 | Apr 26 – May 15 |
| Rhode Island | April 25 | Apr 27 – May 16 |
| Connecticut | April 25 | Apr 27 – May 16 |
| New York | May 1 | May 3 – May 22 |
Questions gardeners in New Hampshire ask
When is the best time to plant sweet corn in New Hampshire?
Sow sweet corn in New Hampshire between May 15 and June 3. That timing is set by New Hampshire's average last spring frost of May 13.
What is the latest I can plant sweet corn in New Hampshire?
About July 27. Sweet corn needs at least 60 days to mature, and frost around September 25 ends the season, so later plantings risk being cut short.
When will sweet corn planted in New Hampshire be ready to harvest?
Planted on time, sweet corn is usually ready from about July 19 to August 28, 60-100 days after sowing.
When is the last frost in New Hampshire?
On average around May 13, with the first fall frost around September 25 - about 135 frost-free days. Your town may differ by two weeks or more.