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 for gardeners who are itching to dig but the ground is still cold. Seeds pop up in under a week, the young plants shrug off a light frost, and a spring root is ready to pull in three to five weeks. Miss the spring window and there's a second one waiting in late summer, so a bad start doesn't cost you the whole year.
A calendar date is only a starting guess. Weather runs early or late every year, so this guide leans on soil temperature and extension-verified day ranges you can check yourself, not just a month on a page.
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
A soil thermometer beats a calendar. Push one 2 inches down in the morning, before the sun warms the top layer, and check the number against the thresholds below.
| Threshold | Soil temperature | What happens |
|---|---|---|
| Minimum for germination | 40–45 F | Seed will sprout, but slowly and unevenly |
| Best for germination and growth | 50–65 F | Fast, even sprouting; roots size up well |
| Sweet spot for sowing | 55–65 F | The target most gardeners aim for |
| Upper limit for reliable germination | 85–95 F | Sprouting gets weak and unreliable above this |
Cornell University puts radish germination at roughly 45 to 85 F, with the plant growing best in 50 to 65 F weather. Oregon State University Extension gives a wider workable floor, down to 40 F, and says germination becomes unreliable above about 95 F. Either way, the practical target for sowing is the same: soil around 55 to 65 F.
Pro tip
Sow shallow and thin. Drop radish seed about 1/2 inch deep and aim for 2 inches apart in the row, matching the standard radish spacing. 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 much you can stretch the window
If your last frost date already passed, or a hard freeze is coming early, you can push both ends of the radish season. A cold frame extends the spring or fall planting window by about 2 to 4 weeks on each end, per Iowa State University Extension, which names radishes as a good crop for the technique.
A floating row cover works the same idea without a frame. It won't buy you a fixed number of weeks the way a cold frame does, but it adds a few degrees of frost protection over the bed, which is often enough to get one more sowing in before a hard freeze or to start a few weeks earlier than the open-ground date. Lay it loosely over hoops so it doesn't crush the seedlings.
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
Check your soil, not the calendar first: sow once it hits 45 F and you're inside 4 to 6 weeks of your last spring frost. Drop seed 1/2 inch deep, 2 inches apart, and start a new short row every 1 to 2 weeks. When heat settles in for good, stop, and pick the crop back up in late summer for a fall round.
Related reading
- When to harvest radishes — pulling them before they go woody
- How far apart to plant radishes — thinning and spacing by variety
- When to plant carrots — another cool-season root crop with a similar spring/fall split
- Plant spacing calculator — work out seed counts for any bed size
Common questions
What month do you plant radishes?
It depends on your zone. In cold zones (3-5), sow spring radishes April to May. In temperate zones (6-7), sow March to April. In mild zones (8-10), sow as early as February. For fall, sow again 6 to 8 weeks before your first fall frost, which is roughly August in cold zones and September to October in mild zones.
How long after planting are radishes ready?
Spring radish varieties like Cherry Belle are ready in 22 to 35 days, per University of Maryland Extension. Winter and daikon types take much longer, 50 to 70 days, which is why they need an earlier, mid-to-late summer sowing for a fall harvest.
What soil temperature do radishes need to germinate?
Radish seed germinates in soil from about 45 F up through the 80s F, and the plant grows best in cool 50 to 65 F weather, per Cornell University guidance. Oregon State University Extension lists a workable range down to 40 F, with germination becoming unreliable above about 95 F. The practical sweet spot for sowing is soil around 55 to 65 F.
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.
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
- Growing Radishes in Oregon Home Gardens — Oregon State University 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)
Sow carrot seeds 2 to 4 weeks before your last spring frost, once the soil warms past 40 to 45 F. For a fall crop, sow 10 to 12 weeks before the first fall frost. Carrots tolerate light frost and sweeten as the weather cools.
Read →When to Plant Tulip Bulbs (by USDA Zone)
Plant tulip bulbs in fall once soil at 6 inches deep cools to 50-60°F, usually September to November depending on your zone. Warm zones need 6-10 weeks of pre-chilling first.
Read →When to Plant Zucchini (Frost + Soil Temp Timing)
Plant zucchini after your last spring frost, once the soil hits at least 60 F (ideally 65 to 70 F). Direct-sow seeds 1/2 to 1 inch deep, or set out transplants started 2 to 4 weeks earlier. Warm zones get a second fall crop.
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)
Plant swiss chard 2 to 4 weeks before your last spring frost, once the soil hits 40°F. For a full fall crop, sow about 9 to 14 weeks before the first fall frost. Seeds go half an inch to an inch deep.
Read →