If you’re wondering when to plant radishes in Illinois, you’ve come to the right place. Getting the timing right is the single most important step for a crisp, successful harvest.
This guide will walk you through the best planting times for radishes in Illinois, covering both spring and fall planting windows. We’ll also cover how to choose varieties and provide simple care tips to ensure your radishes grow plump and tasty.
When to Plant Radishes in Illinois – Best Planting Times For
Radishes are a cool-season crop, which means they thrive in the cooler temperatures of spring and fall. Illinois gardeners have two primary planting seasons to take advantage of.
Spring Planting in Illinois
For a spring harvest, you can sow radish seeds directly in the garden very early. The soil just needs to be workable—not frozen or soggy.
- Optimal Start Date: As soon as the soil can be worked, typically from late March to mid-April in central Illinois. Southern Illinois can start a week or two earlier, while northern Illinois may need to wait until mid-to-late April.
- Successive Planting: To extend your harvest, plant a new small row every 7-10 days until late spring.
- Spring Deadline: Stop spring plantings by late May. As summer heat arrives, radishes become woody, bitter, and bolt (go to seed) quickly.
Fall Planting in Illinois
Fall is often the best time for growing radishes in Illinois. The cooling temperatures create ideal conditions for sweet, mild roots.
- Optimal Start Date: Begin sowing seeds again in mid-to-late August.
- Main Planting Window: Continue planting through September. In southern Illinois, you can often plant into early October.
- Fall Advantage: Fewer pests, consistent moisture from autumn rains, and less risk of bolting make for an exceptional crop.
Understanding Your Illinois Growing Zone
Illinois spans USDA hardiness zones 5a to 7a. This affects your precise start date.
- Zone 5 (Northern IL): Aim for mid-April for spring planting. Start fall planting in early to mid-August.
- Zone 6 (Central IL): Aim for early April for spring. Start fall planting in mid-to-late August.
- Zone 7 (Southern IL): You can start as early as late March for spring. Fall planting can extend into early October.
A simple soil thermometer is a great tool. Radish seeds germinate best when soil temperatures are between 45°F and 85°F, with 60°F being ideal.
Choosing the Right Radish Variety
Picking a variety suited to the season improves your results. Some radishes handle heat or cold better than others.
Best for Spring & Quick Harvests
- Cherry Belle: The classic round, red radish. Ready in about 22 days.
- French Breakfast: Oblong and mild, maturing in 23-25 days.
- Easter Egg Blend: A mix of colorful round radishes, fun for kids.
Best for Fall & Winter Storage
- Daikon: A large, white winter radish perfect for fall, taking 50-60 days.
- Watermelon Radish: Green on the outside, bright pink inside. Best flavor after a frost.
- Black Spanish: A hardy, pungent radish excellent for storage.
Step-by-Step Planting Guide
Follow these simple steps for a reliable radish crop everytime.
- Prepare the Soil: Choose a sunny spot (at least 6 hours of sun). Loosen the soil to a depth of 8-12 inches and mix in some compost. Remove any large stones.
- Sow the Seeds: Plant seeds ½ inch deep. Space them about 1 inch apart in rows that are 12 inches apart. You can also broadcast seeds in a wide row.
- Water Gently: Keep the soil consistently moist but not waterlogged for best germination, which usually takes 4-7 days.
- Thin Seedlings: Once seedlings are about 2 inches tall, thin them so they are 2-3 inches apart. Crowded radishes won’t form bulbs properly.
Caring for Your Radishes
Radishes are low-maintenance, but a few key care tips ensure a perfect harvest.
- Watering: Provide about 1 inch of water per week. Uneven watering leads to cracked or pithy roots.
- Weeding: Keep the area weed-free to reduce competition for nutrients. Be careful not to disturb the shallow roots of your radishes.
- Fertilizing: Usually not needed if you added compost. Too much nitrogen leads to lush tops and tiny roots.
- Pest Watch: Watch for flea beetles (tiny holes in leaves). Use row covers as a preventative measure. Cabbage root maggot can be a problem in spring; rotating your crops each year helps alot.
Harvesting and Storage Tips
Harvesting at the right time is crucial for texture and flavor.
- When to Harvest: Check your seed packet for “days to maturity.” Most spring radishes are ready in 3-4 weeks. They should be about 1 inch in diameter. Don’t let them sit too long or they get woody.
- How to Harvest: Simply grasp the base of the greens and pull gently. If soil is compacted, use a garden fork to loosen it first.
- Storing Your Harvest: Cut off the greens (they draw moisture from the root). Store unwashed roots in a plastic bag in the fridge for up to two weeks. Winter radishes store well in a cool, humid place like a root cellar.
Common Problems and Solutions
Even easy crops have issues sometimes. Here’s how to fix common radish troubles.
- All Leaf, No Bulb: Usually caused by too much shade, overcrowding, or excessive nitrogen fertilizer.
- Woody or Bitter Taste: Caused by hot weather or leaving them in the ground too long. Stick to the spring/fall windows and harvest promptly.
- Split or Cracked Roots: This is from uneven watering. Try to maintain consistent soil moisture.
- Bolting (Going to Seed): Triggered by warm temperatures. You can’t reverse it, so harvest immediately if you see a flower stalk forming.
Frequently Asked Questions (FAQ)
Can you plant radishes in the summer in Illinois?
It’s not recommended. Summer heat causes radishes to bolt quickly and become unpalatable. For a summer harvest, you would need to use shade cloth and choose bolt-resistant varieties, but success is limited.
How late can you plant radishes in Illinois?
For a fall crop, you can plant until about 4-6 weeks before your first expected hard frost. In central Illinois, where the first frost is often in mid-October, a early September planting is your last best chance.
Can radishes survive a frost?
Yes! Radishes are quite frost-tolerant. A light frost can actually sweeten their flavor. A hard freeze (below 28°F) may damage the tops, but the roots in the ground are often still protected and harvestable.
What are the best companion plants for radishes?
Radishes grow well with lettuce, peas, and cucumbers. They can also help by marking rows for slower-germinating crops like carrots. Some gardeners plant them near squash to deter cucumber beetles.
Why did my radishes not form bulbs?
The most common reasons are planting too close together (not thinning), excessive heat, or soil that is too compacted or stony. Ensure loose soil and proper spacing for the best results.