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When to plant Radish in Danforth, IL

The best window to plant Radish in Danforth, is April 4–April 25, when soil warms to 50°F. Last frost typically hits April 18; first frost October 13. A second sowing from August 4 to August 18 extends the harvest into fall.

When to Plant Radish in Danforth, IL

Iroquois County, Illinois Zone 5b August

August to-do list for Iroquois County, Illinois

August is a pivotal month for Iroquois County, Illinois gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost April 18
Avg. first frost October 13
Soil temp (4") 76°F
Watering Moderate
Pest pressure High
Daylight 13.6 hrs
  1. Kick off the fall garden with radish

    Count back from your first frost (October 13) — these need to mature before the cold arrives.

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Radishes are one of the fastest-growing vegetables, with some varieties ready in under a month. They come in round, elongated, and large winter types.

Danforth, Illinois is in USDA Zone 5b. The average last spring frost is April 18 and the first fall frost is October 13, giving you a growing season of approximately 178 days.

At an elevation of 1,345 feet, Iroquois County receives approximately 30 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Radish during the growing season.

Danforth, IL (Zone 5b) Moderate season
178 days
Last Spring Frost April 18
178 growing days
First Fall Frost October 13

Danforth Soil Profile

Soil Type

Silt Loam

Soil pH

5.9-6.7

Drainage

Well Drained

Radish Planting Risk Windows

Early Start (70% safe) ✓ Fits season (129 days to spare)
Transplant: Apr 13 🍅 Harvest: May 11 – Jun 1
Recommended (50%) ✓ Fits season (129 days to spare)
Transplant: Apr 18 🍅 Harvest: May 16 – Jun 6
Safe Start (90%) ✓ Fits season (127 days to spare)
Transplant: May 6 🍅 Harvest: Jun 3 – Jun 24

Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.

Soil Compatibility in Danforth

How your county's soil matches Radish's growing requirements.

Soil pH

Your soil pH (5.9–6.7) overlaps with Radish's range (6.0–7.0), though not a perfect match.

Soil Texture

The silt loam soil in Iroquois County is excellent for Radish — good drainage, moisture retention, and nutrient holding capacity.

Drainage

Drainage is adequate for Radish.

Organic Matter

Organic matter is excellent (4.5%) — Radish will thrive.

How to Plant Radish

0.5"
Planting Depth
2"
Between Plants
6"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Radish

10
successive plantings in your 178-day season

Sow every 2.4 weeks. Last sowing by Sep 08 to harvest before frost.

For a dedicated fall crop, sow by Aug 04.

Radish Water Budget

Plant needs
0.5″/week
Rainfall provides
0.7″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Radish

Radish needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.

Month Radish Needs Rainfall You Supplement Action
Jan 1.3" 0" ❄️ Dormant
Feb 1.4" 0" ❄️ Dormant
Mar 1.9" 0" ❄️ Dormant
Apr 2.2" 2.8" 0" ✅ Rainfall sufficient
May 2.2" 3.8" 0" ✅ Rainfall sufficient
Jun 2.2" 3.6" 0" ✅ Rainfall sufficient
Jul 2.2" 3" 0" ✅ Rainfall sufficient
Aug 2.2" 2.9" 0" ✅ Rainfall sufficient
Sep 2.2" 3.2" 0" ✅ Rainfall sufficient
Oct 2.2" 2.5" 0" ✅ Rainfall sufficient
Nov 2" 0" ❄️ Dormant
Dec 1.6" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Oct in Iroquois County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Radish Heat Requirements (GDD)

What are Growing Degree Days (GDD)?

Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.

Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.

Radish needs ~392 GDD — county provides 2,447 GDD Excellent fit

Radish Planting Timeline — Danforth, IL

Radish Planting Calendar

Activity When Date Range
Direct Sow April 4 Apr 4 – Apr 25
Harvest May 2 May 2 – May 23
Fall Sowing August 4 Aug 4 – Aug 18

Plant 0.5" deep · 2" apart · Rows 6" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Direct Sow
May Harvest
June
July
August Fall Sowing
September
October
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.5"/week · Natural rainfall sufficient

📅 Days to Maturity

22–35 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 5b

📆 Growing Season

178 days in Iroquois County

Growing Tips for Radish in Danforth

Direct sow Radish outdoors after April 18 in Iroquois County when soil has warmed and frost danger has passed.

Your generous 178.0-day season in Iroquois County allows multiple plantings of Radish. Sow every 11.0 days for continuous harvest.

Common pests for Radish in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow every 1-2 weeks for continuous harvest. Do not transplant. Harvest spring radishes promptly to prevent them from becoming pithy and hot.

Companion Planting

Good Companions

Avoid Planting Near

  • Hyssop

Check more plant combinations with our Companion Planting Checker →

When should I plant Radish in Danforth, IL?

In Danforth, IL, plant Radish after the last frost (around April 18) and before the first frost (around October 13). Best results when soil holds above 50°F.

What growing zone is Danforth, IL for Radish?

Danforth sits in USDA Zone 5b. Radish grows reliably in zones 2a through 11b, so it's a good fit here.

Can Radish grow in Danforth's climate?

Yes — Radish grows well in Danforth's temperate climate. Danforth averages a 178-day frost-free season, with last frost around April 18 and first frost around October 13.

🌱

Your Iroquois County Garden Planner — Free

A 22-page printable planner built for Iroquois County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Iroquois County, IL. Local conditions may vary. Last updated: August 2026.