When to plant radishes 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). Radish needs 22–30 days to mature, which fits comfortably within New Hampshire's growing season.
When to plant radishes in New Hampshire: the short answer
For a spring planting, sow Apr 10 – Apr 29. Seeds germinate in soil from 40 to 85°F.
Succession sow again in New Hampshire: Apr 25 · May 5 · May 15 · May 25 · Jun 4 · Jun 14
Spring succession stops before summer heat makes it bolt. Start sowing again in late summer for a fall crop (see the fall window above).
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 radishes in New Hampshire, step by step
- Prepare the bed. They need six or more hours of sun for the best growth, though four to six hours in partial shade is enough and loose soil at least 6 inches deep, with a pH between 6.0 and 7.0. Dig in compost before planting.
- Sow outdoors (Apr 10 – Apr 29). Space plants about 2 inches apart in rows 6 inches apart, sowing seed ½ inch deep. It handles frost well, so it can go out before the last frost date. As a cool-season crop it does best before summer heat arrives in New Hampshire.
- 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: flea beetle, cabbage root maggot, aphids. Diseases and disorders: clubroot, scab, downy mildew.
- Harvest (from about May 7 – May 15). Radish takes 22-30 days to reach harvest. The classic marker crop and quick filler. Sow a short row every 10 days - a single big sowing all matures at once and then goes pithy and hot.
Figures come from our crop data; dates use New Hampshire’s average frost dates. More in the full radish growing guide.
Radish 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 radish dates shift with them.
When to plant radishes in nearby states
| State | Last frost | Sow |
|---|---|---|
| New Hampshire (this page) | May 13 | Apr 10 – Apr 29 |
| Maine | May 14 | Apr 11 – Apr 30 |
| Vermont | May 14 | Apr 11 – Apr 30 |
| Massachusetts | April 24 | Mar 22 – Apr 10 |
| Rhode Island | April 25 | Mar 23 – Apr 11 |
| Connecticut | April 25 | Mar 23 – Apr 11 |
| New York | May 1 | Mar 29 – Apr 17 |
Questions gardeners in New Hampshire ask
When is the best time to plant radishes in New Hampshire?
Sow radishes in New Hampshire between April 10 and April 29. That timing is set by New Hampshire's average last spring frost of May 13.
Can I plant radishes in the fall in New Hampshire?
Yes. For a fall crop, sow between August 11 and August 28, so the crop matures in cool weather before New Hampshire's first frost around September 25.
When will radishes planted in New Hampshire be ready to harvest?
Planted on time, radishes are usually ready from about May 7 to May 15, 22-30 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.