When to Plant Radicchio in Washington County, ID
This month in Washington County, Idaho
May is a pivotal month for Washington County, Idaho gardens. Focus on these tasks first and you'll set up the rest of the season for success.
-
Time to transplant radicchio
Your last frost (May 9) has passed. These warm-season crops can handle outdoor soil now.
June prep starts now
- Starting indoors: radicchio
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.
Washington County, Idaho is in USDA Zone 7a. The average last spring frost is May 9 and the first fall frost is October 1, giving you a growing season of approximately 145 days.
At an elevation of 4,048 feet, Washington County receives approximately 17.9 inches of rainfall annually with predominantly loam soil. Summer highs average 85°F, providing good warmth for Radicchio during the growing season. With low rainfall, drip irrigation is essential for growing Radicchio successfully. Mulch heavily to conserve soil moisture.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.8
Drainage
Well Drained
Plant Planting Risk Windows
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 Washington County
How your county's soil matches Radicchio's growing requirements.
Soil pH
Your soil pH (6.2–7.8) overlaps with Radicchio's range (6.0–7.0), though not a perfect match.
Soil Texture
The loam soil in Washington 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 (2.5%). Annual compost additions will help Radicchio.
How to Plant Radicchio
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Radicchio
Sow every 6.9 weeks. Last sowing by Jul 13 to harvest before frost.
For a dedicated fall crop, sow by Jul 23.
Plant Water Budget
Water stress score is 6/10 — 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 | — | 1.1" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 1.9" | 0" | ❄️ Dormant |
| Apr | — | 1.7" | 0" | ❄️ Dormant |
| May | 3" | 2" | 1" | 💧 Light watering |
| Jun | 3" | 1.2" | 1.8" | 🚿 Regular watering |
| Jul | 3" | 1.6" | 1.4" | 💧 Light watering |
| Aug | 3" | 1.7" | 1.3" | 💧 Light watering |
| Sep | 3" | 1.5" | 1.5" | 🚿 Regular watering |
| Oct | 3" | 1.5" | 1.5" | 🚿 Regular watering |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Washington 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 Planting Timeline — Washington County, ID
Radicchio Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 4 | Apr 4 – Apr 18 |
| Transplant Outdoors | May 9 | May 9 – May 23 |
| Direct Sow | April 25 | Apr 25 – May 16 |
| Harvest | July 11 | Jul 11 – Aug 15 |
| Fall Sowing | July 23 | Jul 23 – Aug 6 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| 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: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
145 days in Washington County
Growing Tips for Radicchio in Washington County
Direct sow Radicchio outdoors after May 09 in Washington 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
Check more plant combinations with our Companion Planting Checker →
Radicchio in Other Locations
Frequently Asked Questions
When should I plant Radicchio in Washington County, ID?
Washington County is in Zone 7a with an average last frost of May 9. Plan your Radicchio planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, ID?
Washington County, Idaho is in USDA Hardiness Zone 7a. The average last spring frost is May 9 and first fall frost is October 1.
Your Washington County Garden Planner — Free
A 24-page printable planner built for Washington County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.