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Vegetable Crop Calendars (A–C)Radish Planting Calendar: Fast Crop Succession
Radishes are ready in a few weeks and turn bad within days of their peak. That makes small, frequent plantings the only sensible way to grow them.
Key points
- Sow small batches every 7 to 10 days, or every one to two weeks.
- Plan for roughly three to five weeks to harvest for garden types.
- Skip sowing in sustained summer heat.
- Harvest on time; late roots turn pithy and hot.
How often should you sow radishes?
Iowa State Extension recommends a new batch every 7 to 10 days so only a few roots mature each week. Alabama Extension suggests every one to two weeks. Both agree on the same principle: small, steady sowings beat one big one.
A good practice is to sow a short row each time, say a few feet, and note the date in a garden journal. Stop when your climate heats up.
For example, if you sow on the first Saturday of April and every Saturday after that, you will have a rolling harvest from late April through early June, adjusted to your local weather.
How fast do radishes mature?
Iowa State reports about three to five weeks from planting for garden radishes, while Alabama Extension says about 25 to 30 days, with roots roughly one to one and a half inches across. Daikon and other big radishes take longer, 7 to 10 weeks in Iowa's account.
Varieties differ, so check the packet. Count the days for your variety rather than guessing, and begin tasting when roots hit the size on the label.
Interplanting works too. Radishes sown alongside slower crops are out of the bed before the slow crop needs the space.
When do you plant radishes in spring and fall?
Iowa State's timing is early April sowing, then every 7 to 10 days through mid-May, with fall sowings from early to mid-August through mid-September. Alabama Extension describes two windows in that state: late winter (February to March) and early fall (September to mid-October).
The gap between those regions shows why the calendar must be local. Use frost dates and heat as your limits: sow once soil is workable and stop before sustained hot weather.
Plant seed shallow in loose soil and keep the surface moist. Radishes germinate quickly in cool weather, so you will see sprouts within days rather than weeks.
What happens in summer heat?
Iowa State says summer heat makes radishes spongy, woody and overly hot, and plants bolt. It advises avoiding the crop during that period.
If you want a summer radish, look for heat-tolerant types suggested by local extension, and give them afternoon shade and steady moisture. Expect mixed results.
Cool, moist soil produces milder roots, so shade and mulch can stretch the season a little in warm spells. Where nights stay cool but days warm early, try shading the row with a cloth during the afternoon so soil does not bake.
Why do some radishes make only leaves?
Iowa State notes that sudden hot weather or excess nitrogen can give you big tops and little root. Use a soil test and local recommendations rather than extra feeding.
Thin seedlings early. Crowded plants compete and produce small or misshapen roots. Even moisture also helps prevent cracking.
Large radishes such as daikon take much longer, so give them their own space and timeline instead of mixing them into your quick rows. Keep a record of which sowing produced the best roots. Over a season or two the notes tell you your local sweet spot better than any general chart, and they show when your own heat arrives.
When should you harvest?
Pull radishes promptly. Iowa State warns that late harvest makes them pithy and hot. Radishes held in the ground past peak lose quality quickly.
Wash and refrigerate after harvest. Leave a bit of top for the first day if you like, then trim to keep roots crisp.
Hold harvested radishes in the refrigerator and use them within a few days for the best texture.
How do you plan a radish succession calendar?
Build the calendar from limits, not from a target number of sowings. The first limit is workable soil in spring and the second is the start of sustained heat. The fall limit is the reverse: begin when heat eases and stop when cold ends growth.
Use this plan:
Flea beetles and root maggots can damage radishes in some areas. Floating row cover at sowing is a physical barrier, and your extension office can advise on other options and legal use.
- List your spring window from workable soil to the first hot spell.
- Divide it into weekly or ten-day sowing dates.
- Mark a summer gap and rest the bed or plant a heat-loving crop.
- List your fall window from easing heat to a hard freeze.
- Record actual days to harvest for your variety and adjust next year.
Timing at a glance
| Item | Window | Caveat |
|---|---|---|
| Radishes, Iowa spring | Sow early April, then every 7 to 10 days through mid-May | Iowa State guidance; adjust for your own last frost and soil. |
| Radishes, Iowa fall | Sow early to mid-August, then every 7 to 10 days through mid-September | Iowa State guidance; check your first fall frost. |
| Radishes, Alabama | February to March and September to mid-October | Alabama Extension; local frost and heat vary. |
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.