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When to Plant Fennel in Teton County, MT

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.

Teton County, Montana is in USDA Zone 4a. The average last spring frost is May 25 and the first fall frost is September 16, giving you a growing season of approximately 114 days.

At an elevation of 8,276 feet, Teton County receives approximately 15.1 inches of rainfall annually with predominantly loam soil. Summer highs average 84ยฐF, so choose short-season varieties of Fennel to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Fennel successfully. Mulch heavily to conserve soil moisture.

Teton County, MT (Zone 4a) Short season
114 days
Last Spring Frost May 25
114 growing days
First Fall Frost September 16

Teton County Soil Profile

Soil Type

Loam

Soil pH

6.6-7.6

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 18 Transplant: Jun 10 🍅 Harvest: Aug 12 – Sep 23
Recommended (50%) ✗ May not fit
Start indoors: Mar 23 Transplant: Jun 15 🍅 Harvest: Aug 17 – Sep 28
Safe Start (90%) ✗ May not fit
Start indoors: Apr 9 Transplant: Jul 2 🍅 Harvest: Sep 3 – Oct 15

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.6″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 905 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Fennel needs ~975 GDD — county provides 1,482 GDD Excellent fit

Fennel Planting Timeline โ€” Teton County, MT

Fennel Planting Calendar

Activity When Date Range
Start Indoors March 23 Mar 23 โ€“ Apr 6
Transplant Outdoors June 15 Jun 15 โ€“ Jun 29
Direct Sow June 8 Jun 8 โ€“ Jun 29
Harvest August 17 Aug 17 โ€“ Sep 28

Plant 1" deep ยท 15" apart ยท Rows 24" apart

Month-by-Month Timeline

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

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

60โ€“90 days

Soil pH

5.5 โ€“ 7

USDA Zone

Zone 4a

Growing Season

114 days

Growing Tips for Teton County

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

  • Tomatoes
  • Peppers
  • Beans

Level Up Your Garden

Frequently Asked Questions

When should I plant Fennel in Teton County, MT?

Teton County is in Zone 4a with an average last frost of May 25. Plan your Fennel planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Teton County, MT?

Teton County, Montana is in USDA Hardiness Zone 4a. The average last spring frost is May 25 and first fall frost is September 16.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Teton County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.

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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 Teton County, MT. Local conditions may vary. Last updated: April 2026.