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When to Plant Radicchio in Amador County, CA

Amador County, California Zone 9b May

Your May planting checklist for Amador County, California

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

Avg. last frost March 8
Avg. first frost November 25
Soil temp (4") 69°F
Watering Critical
Pest pressure High
Daylight 14.1 hrs
  1. It's harvest week for radicchio

    If you can't use it all right away, check the food-preservation section of your planner.

Coming up in June — start thinking about
  • First harvests: 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.

Amador County, California is in USDA Zone 9b. The average last spring frost is March 8 and the first fall frost is November 25, giving you a growing season of approximately 262 days.

At an elevation of 1,335 feet, Amador County receives approximately 42.7 inches of rainfall annually with predominantly loam soil. Summer highs average 89°F, providing good warmth for Radicchio during the growing season.

Amador County, CA (Zone 9b) Long season
262 days
Last Spring Frost March 8
262 growing days
First Fall Frost November 25
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Amador County Soil Profile

Soil Type

Loam

Soil pH

6.7-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (179 days to spare)
Start indoors: Jan 8 Transplant: Feb 5 🍅 Harvest: Apr 9 – May 14
Recommended (50%) ✓ Fits season (164 days to spare)
Start indoors: Feb 8 Transplant: Mar 8 🍅 Harvest: May 10 – Jun 14
Safe Start (90%) ✓ Fits season (146 days to spare)
Start indoors: Mar 22 Transplant: Apr 19 🍅 Harvest: Jun 21 – Jul 26

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 Amador County

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

Soil pH

Your soil pH (6.7–7.8) is more alkaline than Radicchio prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.7%). Annual compost additions will help Radicchio.

How to Plant Radicchio

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

Fall planting: Sow 8 weeks before your first frost date for a fall harvest.

Succession Planting Radicchio

5
successive plantings in your 262-day season

Sow every 6.9 weeks. Last sowing by Sep 06 to harvest before frost.

For a dedicated fall crop, sow by Sep 30.

Plant Water Budget

Plant needs
0.7″/week
Rainfall provides
0.7″/week
You supply
0.0″/week
Watering frequency Only during dry spells
Season total 43 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 9.4" 0" ❄️ Dormant
Feb 8" 0" ❄️ Dormant
Mar 3" 6" 0" ✅ Rainfall sufficient
Apr 3" 3.5" 0" ✅ Rainfall sufficient
May 3" 1" 2" 🚿 Regular watering
Jun 3" 0.2" 2.8" 🚿 Regular watering
Jul 3" 0" 3" 🚿 Regular watering
Aug 3" 0" 3" 🚿 Regular watering
Sep 3" 0.5" 2.5" 🚿 Regular watering
Oct 3" 1.9" 1.1" 💧 Light watering
Nov 3" 4.3" 0" ✅ Rainfall sufficient
Dec 7.8" 0" ❄️ Dormant

Water needs are for active growing months only (Mar–Nov in Amador 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 ~1,172 GDD — county provides 4,388 GDD Excellent fit

Radicchio Planting Timeline — Amador County, CA

Radicchio Planting Calendar

Activity When Date Range
Start Indoors February 8 Feb 8 – Feb 22
Transplant Outdoors March 8 Mar 8 – Mar 22
Direct Sow February 15 Feb 15 – Mar 8
Harvest May 10 May 10 – Jun 14
Fall Sowing September 30 Sep 30 – Oct 14

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.7"/week · Only during dry spells

📅 Days to Maturity

60–80 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9b

📆 Growing Season

262 days in Amador County

Growing Tips for Radicchio in Amador County

Direct sow Radicchio outdoors after March 08 in Amador 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 Amador County, CA?

Amador County is in Zone 9b with an average last frost of March 8. Plan your Radicchio planting based on this frost date — see the calendar above for exact timing.

What planting zone is Amador County, CA?

Amador County, California is in USDA Hardiness Zone 9b. The average last spring frost is March 8 and first fall frost is November 25.

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Your Amador County Garden Planner — Free

A 24-page printable planner built for Amador County (Zone 9b). 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 Amador County, CA. 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.