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Historical frost averages plus extension guidance, not a forecast. Check the forecast and soil temperature before planting.
Sow radishes outside from about 6 weeks before your last spring frost until a week before it. Sow again for fall 6–8 weeks before your first fall frost. Radishes are hardy, fast, and best grown in cool weather.
- Frost tolerance
- Hardy: takes frost
- Soil temperature
- Sows at 45–90°F (min 40°F)
- Days to harvest
- 20–35 days (spring types)
The rule we use
- Sow outdoors: 1–6 weeks before the last spring frost
- Sow for fall: 6–8 weeks before the first fall frost
Fast and early
Radishes are the quickest crop in most gardens. Spring varieties are ready in 3–5 weeks, and seed sprouts in soil as cool as 40°F. Sow ½ inch deep and thin seedlings to about 1–2 inches apart, or the roots won't swell.
Sow a short row every week or two rather than all at once. A radish left in the ground too long turns pithy and hot.
Why radishes fail
Heat is the main problem. Warm weather and long days make radishes bolt and turn woody, so spring radishes should be sown early. Dry soil also makes them hot and tough; keep it evenly moist.
If you get leaves but no roots, the plants are usually crowded or shaded. Radishes need sun and room.
Fall radishes
Spring types do well again in fall, sown 6–8 weeks before your first fall frost. Larger winter radishes such as daikon need longer, about 50–70 days, and keep well in cool weather.
Radishes are useful as markers too. Sow a few seeds along a row of slow carrots or parsnips: the radishes come up first, show you where the row is, and are pulled before the carrots need the space.
Seeds and supplies for radishes
- Radish seeds at True Leaf Market
- Park Seed for seeds and young plants.
- A soil thermometer to check the soil is warm enough before sowing.
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Questions about planting radishes
How early can you plant radishes?
About 6 weeks before your last spring frost, once the soil can be worked. Enter your ZIP above for dates.
Can radishes grow in summer?
Spring varieties usually bolt and turn woody in summer heat. Wait and sow again in late summer for fall.
How long do radishes take to grow?
Most spring radishes take 3–5 weeks. Winter types like daikon take about 7–10 weeks.
Sources
- Vegetable Planting Calendar for Central Maryland (2026), University of Maryland Extension
- Vegetables for Spring and Fall Planting; Vegetables for Summer Planting, University of Maryland Extension Master Gardeners
- Suggested Vegetable Planting Dates for Utah, Utah State University Extension
- Vegetable Planting Guide (CMG GardenNotes #720), Colorado State University Extension
- Soil temperature conditions for vegetable seed germination, Oregon State University Extension
- Frost dates: NOAA NCEI U.S. Climate Normals 1991–2020 (doi:10.25921/4ek7-fk11)