When to plant radishes in Utah
Utah’s average last spring frost is May 5, and the first fall frost typically arrives around October 5 — about 153 frost-free days (USDA zones 4a, 5a, 5b, 6b, 7b, 8a, 9a). Radish needs 22–30 days to mature, which fits comfortably within Utah's growing season.
Utah covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant radishes in Utah: the short answer
For a spring planting, sow Apr 2 – Apr 21. Seeds germinate in soil from 40 to 85°F.
Succession sow again in Utah: Apr 17 · Apr 27 · May 7 · May 17 · May 27 · Jun 6
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 Utah, 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 2 – Apr 21). 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 Utah.
- 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 Apr 29 – May 7). 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 Utah’s average frost dates. More in the full radish growing guide.
Radish planting dates by USDA zone in Utah
Utah spans USDA zones 4a, 5a, 5b, 6b, 7b, 8a, 9a. 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.
| Zone | Last frost | First frost | Season | Start indoors | Plant radish |
|---|---|---|---|---|---|
| Zone 4 | May 10 | Sep 25 | 135 days | - | Apr 7 – Apr 26 |
| Zone 5 | Apr 30 | Oct 5 | 160 days | - | Mar 28 – Apr 16 |
| Zone 6 | Apr 15 | Oct 15 | 185 days | - | Mar 13 – Apr 1 |
| Zone 7 | Apr 5 | Oct 25 | 200 days | - | Mar 3 – Mar 22 |
| Zone 8 | Mar 20 | Nov 5 | 230 days | - | Feb 15 – Mar 6 |
| Zone 9 | Feb 20 | Nov 30 | 280 days | - | Jan 18 – Feb 6 |
When to plant radishes in nearby states
Questions gardeners in Utah ask
When is the best time to plant radishes in Utah?
Sow radishes in Utah between April 2 and April 21. That timing is set by Utah's average last spring frost of May 5; Utah spans several climates, so cooler and higher parts of the state run later.
Can I plant radishes in the fall in Utah?
Yes. For a fall crop, sow between August 21 and September 7, so the crop matures in cool weather before Utah's first frost around October 5.
When will radishes planted in Utah be ready to harvest?
Planted on time, radishes are usually ready from about April 29 to May 7, 22-30 days after sowing.
When is the last frost in Utah?
On average around May 5, with the first fall frost around October 5 - about 153 frost-free days. Your town may differ by two weeks or more.