Harvest guide
When to Plant Radishes (Spring and Fall Timing)
Plant radishes 4 to 6 weeks before your last spring frost, as soon as the soil reaches about 45 F. Spring types mature in 22 to 35 days. Sow again in late summer for a fall crop, and reseed every 1 to 2 weeks.
Days to maturity
22–35days
Ready when
Root ~1in across; pull promptly to avoid woodiness
The short answer
Plant radishes 4 to 6 weeks before your last spring frost, as soon as the soil can be worked and reaches about 45 F. Spring types mature in 22 to 35 days. They grow best in cool 50 to 65 F weather, so sow again in late summer for a fall crop, and reseed every 1 to 2 weeks.
Radishes are the crop you plant when you are itching to start but the soil is still cold. They sprout in days, shrug off a light frost, and a spring type is ready to pull in about three to five weeks. Get them in early, before heat arrives, and you can grow two crops a year. This guide covers when to sow by season and climate, the soil-temperature cue, and how to keep them coming.
When to plant radishes by season and zone
The rule is simple: radishes want cool soil, not cold and not hot. Sow spring radishes 4 to 6 weeks before your average last frost, as soon as the ground can be worked. University of Maryland Extension says to plant as soon as the soil is workable in spring, and notes radishes withstand frost in spring and fall.
Colder zones reach workable soil later, so they sow later. The windows below are starting points. Watch your own frost date and soil more than the calendar.
| Region / zone | Spring sowing | Fall sowing |
|---|---|---|
| Cold (zones 3–5) | April – May | Aug (winter types), late Aug – Sept (spring types) |
| Temperate (zones 6–7) | March – April | Aug – Sept |
| Mild (zones 8–10) | Feb – March | Sept – Oct, plus winter sowing |
University of Minnesota Extension times the spring window to roughly 3 to 6 weeks before the average last frost. Shift earlier as you go south and milder, later as you go north and colder.
The soil-temperature cue
Soil temperature tells you it is time better than any date. Radish seed germinates in cool soil, roughly 45 to 85 F, and the plant grows best in 50 to 65 F weather, per Cornell University guidance.
The practical target is soil around 55 to 65 F when you sow. Cold soil below 45 F just sits there and germinates slowly. Push a cheap soil thermometer 2 inches down in the morning to check.
Pro tip
Sow shallow and thin. Drop radish seed about 1/2 inch deep and aim for 2 inches apart in the row, which matches the radish spacing guide. Crowded radishes make leaves and never size up a root. Thin to one plant every 2 inches as soon as the seedlings are up.
Days to maturity by type
How fast a radish finishes drives when you plant it. Quick spring radishes like Cherry Belle race to the table. Winter and daikon types take far longer and need an earlier sowing.
| Type | Days to maturity | When to sow |
|---|---|---|
| Spring (Cherry Belle, Easter Egg) | 22–35 days | Early spring, again in early fall |
| Winter / daikon (Daikon, Watermelon) | 50–70 days | Mid to late summer for fall |
The 22 to 35 day range for spring types matches our radish crop data, and University of Maryland Extension lists 25 to 35 days for common radishes. Because spring types finish so fast, the harvest window is short, which is exactly why you stagger the sowings.
Spring vs fall, and how to succession plant
Radishes give you two clean seasons and a gap. Spring is the first window, before heat. Fall is the second, after the worst heat breaks. The summer middle is too hot for good roots.
For a steady supply, sow a short row every 1 to 2 weeks through each cool stretch rather than one big planting. UMN Extension recommends small repeat sowings for a continuous harvest. A 3-foot row reseeded every week or two beats one long row that all matures at once and turns woody before you can eat it.
For fall, sow quick spring radishes 4 to 6 weeks before your first fall frost as the soil cools. Plant slower winter and daikon types earlier, in mid to late summer, so they finish before a hard freeze. University of Illinois Extension lists radishes among the reliable cool-season crops for a fall garden.
Common mistake
The big one is planting too late into heat, not too early into cold. Radishes handle frost, but once daytime weather settles into the mid-60s F and warmer they bolt, sending up a flower stalk before the root sizes up, and the roots turn woody and sharp. The other miss is sowing too thick, which gives you all tops and no bottoms. Sow thin, sow early, and reseed in fall.
How to tell it is time to sow
You do not need a perfect date. Three signs say go:
- The soil is workable and not soggy when you squeeze a handful.
- A soil thermometer reads at least 45 F two inches down, ideally 55 to 65 F.
- You are still 4 to 6 weeks out from your last spring frost, or 4 to 6 weeks out from the first fall frost.
If all three line up, sow. A light frost after the seedlings emerge is fine, since young radishes take it without harm.
Your next step
Plant radishes in cool soil: 4 to 6 weeks before your last spring frost, once the ground hits about 45 F, then again in late summer for fall. Sow 1/2 inch deep, 2 inches apart, and reseed a short row every 1 to 2 weeks so they never all come due at once.
Sowing is half the job. The other half is pulling them at the right moment before they get woody, which is covered in when to harvest radishes.
Common questions
When should I plant radishes?
Plant spring radishes 4 to 6 weeks before your last spring frost, as soon as the soil can be worked and reaches about 45 F. University of Maryland Extension says sow as soon as the soil is workable, and notes radishes withstand frost. For a fall crop, sow again in late summer as the soil cools.
What soil temperature do radishes need to germinate?
Radish seed germinates in cool soil, roughly 45 to 85 F, and grows best in cool 50 to 65 F weather, per Cornell University guidance. The sweet spot for planting is soil around 55 to 65 F. Germination slows in very cold soil and quality drops once it turns hot.
How late can you plant radishes in spring?
Stop sowing spring radishes once daytime weather settles into the mid-60s F and warmer. Heat makes radishes bolt, sending up a flower stalk before the root sizes up, and turns the roots woody and sharp. Pick the crop back up in late summer for fall.
Can you plant radishes in the fall?
Yes. Sow quick spring radishes about 4 to 6 weeks before your first fall frost as the soil cools. Plant slower winter and daikon radishes earlier, in mid to late summer, since they need 50 to 70 days. University of Illinois Extension lists radishes among reliable fall crops.
How often should I plant radishes for a steady supply?
Sow a short row every 1 to 2 weeks through the cool stretches of spring and fall. Radishes mature fast, in 22 to 35 days for spring types, so small repeat sowings give a steady harvest instead of one big flush that turns woody before you can eat it.
Sources
Agronomic claims in this guide are checked against these primary sources.
- Growing radishes in home gardens — University of Minnesota Extension
- Growing Radishes in a Home Garden — University of Maryland Extension
- Growing Guide - Radishes — Cornell University Home Gardening
- Cool-season crops for fall — University of Illinois Extension
Keep reading
When to Harvest Radishes (Signs They're Ready)
Salad radishes are ready fast, about 22 to 35 days after sowing, when the root is roughly 1 inch across at the soil line. Pull promptly, check the shoulder, and learn how daikon and winter types differ.
Read →When to Plant Carrots (Spring and Fall Timing by Zone)
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Read →When to Plant Zucchini (Frost + Soil Temp Timing)
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Read →When to Plant Tomatoes (Frost + Soil Temp by Zone)
Set tomato transplants out 1 to 2 weeks after your last spring frost, once soil hits at least 60 F. Start seeds indoors 6 to 8 weeks before that frost date. Cold soil stalls them, so wait for warmth.
Read →When to Plant Swiss Chard (Spring and Fall Timing)
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Read →When to Plant Sweet Potatoes (Soil Temp + Frost Timing)
Plant sweet potato slips 2 to 4 weeks after your last spring frost, once soil holds above 65°F. Get timing by zone, the soil-temp gate, and the mistake that rots slips in cold ground.
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