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When to Plant Radicchio in Shoshone County, ID

Shoshone County, Idaho Zone 6b May

Your May game plan for Shoshone County, Idaho

Your Shoshone County, Idaho garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost May 10
Avg. first frost September 26
Soil temp (4") 41°F
Watering High
Pest pressure Low
Daylight 14.9 hrs
  1. Harden off and plant radicchio

    Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.

June will be here before you know it — start on
  • Starting indoors: radicchio

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Radicchio is an Italian chicory with stunning red and white leaves and a pleasantly bitter flavor. It forms tight heads and is used in salads, grilled, or braised.

Shoshone County, Idaho is in USDA Zone 6b. The average last spring frost is May 10 and the first fall frost is September 26, giving you a growing season of approximately 139 days.

At an elevation of 6,353 feet, Shoshone County receives approximately 14.1 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Radicchio to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Radicchio successfully. Mulch heavily to conserve soil moisture.

Shoshone County, ID (Zone 6b) Short season
139 days
Last Spring Frost May 10
139 growing days
First Fall Frost September 26

Shoshone County Soil Profile

Soil Type

Loam

Soil pH

6.6-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (36 days to spare)
Start indoors: Mar 29 Transplant: May 3 🍅 Harvest: Jul 5 – Aug 9
Recommended (50%) ✓ Fits season (41 days to spare)
Start indoors: Apr 5 Transplant: May 10 🍅 Harvest: Jul 12 – Aug 16
Safe Start (90%) ✓ Fits season (44 days to spare)
Start indoors: Apr 30 Transplant: Jun 4 🍅 Harvest: Aug 6 – Sep 10

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 Shoshone County

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

Soil pH

Your soil pH (6.6–7.7) is more alkaline than Radicchio prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Shoshone County is excellent for Radicchio — good drainage, moisture retention, and nutrient holding capacity.

Drainage

Drainage is adequate for Radicchio.

Organic Matter

Organic matter is moderate (2.8%). Annual compost additions will help Radicchio.

How to Plant Radicchio

0.5"
Planting Depth
6"
Between Plants
12"
Between Rows

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

Succession Planting Radicchio

2
successive plantings in your 139-day season

Sow every 6.9 weeks. Last sowing by Jul 08 to harvest before frost.

For a dedicated fall crop, sow by Jul 18.

Plant Water Budget

Plant needs
0.7″/week
Rainfall provides
0.4″/week
You supply
0.6″/week
Watering frequency 1-2 times/week
Season total 718 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Radicchio

Radicchio needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.

Month Radicchio Needs Rainfall You Supplement Action
Jan 1" 0" ❄️ Dormant
Feb 0.7" 0" ❄️ Dormant
Mar 1.2" 0" ❄️ Dormant
Apr 1.3" 0" ❄️ Dormant
May 3" 1.9" 1.1" 💧 Light watering
Jun 3" 0.9" 2.1" 🚿 Regular watering
Jul 3" 1.2" 1.8" 🚿 Regular watering
Aug 3" 1.5" 1.5" 🚿 Regular watering
Sep 3" 1.3" 1.7" 🚿 Regular watering
Oct 1.2" 0" ❄️ Dormant
Nov 0.9" 0" ❄️ Dormant
Dec 0.9" 0" ❄️ Dormant

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

Radicchio 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.

Radicchio needs ~910 GDD — county provides 1,807 GDD Excellent fit

Radicchio Planting Timeline — Shoshone County, ID

Radicchio Planting Calendar

Activity When Date Range
Start Indoors April 5 Apr 5 – Apr 19
Transplant Outdoors May 10 May 10 – May 24
Direct Sow April 26 Apr 26 – May 17
Harvest July 12 Jul 12 – Aug 16
Fall Sowing July 18 Jul 18 – Aug 1

Plant 0.5" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.7"/week · 1-2 times/week

📅 Days to Maturity

60–80 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 6b

📆 Growing Season

139 days in Shoshone County

Growing Tips for Radicchio in Shoshone County

Direct sow Radicchio outdoors after May 10 in Shoshone County when soil has warmed and frost danger has passed.

Common pests for Radicchio in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.

General growing tips

Start in late summer for fall harvest. The red color develops with cool nights and light frost. Harvest when heads are firm and compact.

Companion Planting

Good Companions

Avoid Planting Near

  • Fennel

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Radicchio in Shoshone County, ID?

Shoshone County is in Zone 6b with an average last frost of May 10. Plan your Radicchio planting based on this frost date — see the calendar above for exact timing.

What planting zone is Shoshone County, ID?

Shoshone County, Idaho is in USDA Hardiness Zone 6b. The average last spring frost is May 10 and first fall frost is September 26.

🌱

Your Shoshone County Garden Planner — Free

A 24-page printable planner built for Shoshone County (Zone 6b). 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 Shoshone County, ID. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.