When to Plant Fennel in Glenn County, CA
Florence fennel is grown for its swollen bulb-like stem base, which has a mild anise flavor. It is crisp raw in salads and sweet when roasted or braised.
Glenn County, California is in USDA Zone 9a. The average last spring frost is March 6 and the first fall frost is November 28, giving you a growing season of approximately 267 days.
At an elevation of 270 feet, Glenn County receives approximately 27.1 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Fennel during the growing season.
Glenn County Soil Profile
Soil Type
Loam
Soil pH
6.5-7.9
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 Glenn County
How your county's soil matches Fennel's growing requirements.
Soil pH
Your soil pH (6.5–7.9) is more alkaline than Fennel prefers (5.5–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Glenn County is excellent for Fennel — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.0%). Annual compost additions will help Fennel.
How to Plant Fennel
Succession Planting Fennel
Sow every 6.9 weeks. Last sowing by Aug 30 to harvest before frost.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Fennel
Fennel needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.
| Month | Fennel Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 5.6" | 0" | ❄️ Dormant |
| Feb | — | 5.3" | 0" | ❄️ Dormant |
| Mar | 2.6" | 4.4" | 0" | ✅ Rainfall sufficient |
| Apr | 2.6" | 2.5" | 0.1" | 💧 Light watering |
| May | 2.6" | 0.7" | 1.9" | 🚿 Regular watering |
| Jun | 2.6" | 0.1" | 2.5" | 🚿 Regular watering |
| Jul | 2.6" | 0" | 2.6" | 🚿 Regular watering |
| Aug | 2.6" | 0" | 2.6" | 🚿 Regular watering |
| Sep | 2.6" | 0.3" | 2.3" | 🚿 Regular watering |
| Oct | 2.6" | 1.3" | 1.3" | 🚿 Regular watering |
| Nov | 2.6" | 2.5" | 0.1" | 💧 Light watering |
| Dec | — | 4.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Glenn County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Fennel 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.
Fennel Planting Timeline — Glenn County, CA
Fennel Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 23 | Jan 23 – Feb 6 |
| Transplant Outdoors | March 13 | Mar 13 – Mar 27 |
| Direct Sow | March 6 | Mar 6 – Mar 27 |
| Harvest | May 15 | May 15 – Jun 26 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Start Indoors |
| March | Transplant Outdoors Direct Sow |
| April | — |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.6"/week · Only during dry spells
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 5.5–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9a
📆 Growing Season
267 days in Glenn County
Growing Tips for Fennel in Glenn County
Direct sow Fennel outdoors after March 06 in Glenn County when soil has warmed and frost danger has passed.
Common pests for Fennel in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow in late summer for fall harvest to reduce bolting. Hill soil around bulbs as they enlarge. Harvest when bulbs are tennis-ball sized before they elongate.
Companion Planting
Good Companions
Avoid Planting Near
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Fennel in Other Locations
Frequently Asked Questions
When should I plant Fennel in Glenn County, CA?
Glenn County is in Zone 9a with an average last frost of March 6. Plan your Fennel planting based on this frost date — see the calendar above for exact timing.
What planting zone is Glenn County, CA?
Glenn County, California is in USDA Hardiness Zone 9a. The average last spring frost is March 6 and first fall frost is November 28.
Plan Your Garden with Confidence
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