When to Plant Tomatillo in Napa County, CA
Tomatillos are a Mexican staple that produces tart, green fruits enclosed in papery husks. They are essential for salsa verde and green sauces.
Napa County, California is in USDA Zone 9a. The average last spring frost is February 26 and the first fall frost is November 26, giving you a growing season of approximately 273 days.
At an elevation of 449 feet, Napa County receives approximately 35 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Tomatillo during the growing season.
Napa County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.5
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 Napa County
How your county's soil matches Tomatillo's growing requirements.
Soil pH
Your soil pH (6.7–7.5) is more alkaline than Tomatillo prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Napa County is excellent for Tomatillo — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Tomatillo.
Organic Matter
Organic matter is moderate (3.0%). Annual compost additions will help Tomatillo.
How to Plant Tomatillo
Succession Planting Tomatillo
Sow every 6.9 weeks. Last sowing by Sep 02 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Tomatillo
Tomatillo needs approximately 1.1 inches of water per week (4.8" per month). Here's how your county's rainfall compares month by month.
| Month | Tomatillo Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 7.5" | 0" | ❄️ Dormant |
| Feb | 4.8" | 7.8" | 0" | ✅ Rainfall sufficient |
| Mar | 4.8" | 5.8" | 0" | ✅ Rainfall sufficient |
| Apr | 4.8" | 2.3" | 2.5" | 🚿 Regular watering |
| May | 4.8" | 0.8" | 4" | 🚿 Regular watering |
| Jun | 4.8" | 0.2" | 4.6" | 🚿 Regular watering |
| Jul | 4.8" | 0" | 4.8" | 🚿 Regular watering |
| Aug | 4.8" | 0" | 4.8" | 🚿 Regular watering |
| Sep | 4.8" | 0.3" | 4.5" | 🚿 Regular watering |
| Oct | 4.8" | 1.3" | 3.5" | 🚿 Regular watering |
| Nov | 4.8" | 3.3" | 1.5" | 💧 Light watering |
| Dec | — | 5.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Napa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Tomatillo 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.
Tomatillo Planting Timeline — Napa County, CA
Tomatillo Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 15 | Jan 15 – Jan 29 |
| Transplant Outdoors | March 5 | Mar 5 – Mar 19 |
| Direct Sow | February 26 | Feb 26 – Mar 19 |
| Harvest | May 7 | May 7 – Jul 16 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Direct Sow |
| March | Transplant Outdoors Direct Sow |
| April | — |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.1"/week · 2-3 times/week
📅 Days to Maturity
60–85 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9a
📆 Growing Season
273 days in Napa County
Growing Tips for Tomatillo in Napa County
Direct sow Tomatillo outdoors after February 26 in Napa County when soil has warmed and frost danger has passed.
Common pests for Tomatillo in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 6-8 weeks before last frost. Plant at least two plants for cross-pollination. Harvest when fruits fill the husk and it begins to split.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Tomatillo in Other Locations
Frequently Asked Questions
When should I plant Tomatillo in Napa County, CA?
Napa County is in Zone 9a with an average last frost of February 26. Plan your Tomatillo planting based on this frost date — see the calendar above for exact timing.
What planting zone is Napa County, CA?
Napa County, California is in USDA Hardiness Zone 9a. The average last spring frost is February 26 and first fall frost is November 26.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Napa County gardeners in Zone 9a organize planting dates, track what's growing, and never miss a planting window.
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