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When to Plant Fennel in Prairie 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.

Prairie County, Montana is in USDA Zone 4a. The average last spring frost is May 11 and the first fall frost is October 1, giving you a growing season of approximately 143 days.

At an elevation of 6,830 feet, Prairie County receives approximately 22.2 inches of rainfall annually with predominantly loam soil. Summer highs average 81ยฐF, so choose short-season varieties of Fennel to ensure they mature before fall.

Prairie County, MT (Zone 4a) Short season
143 days
Last Spring Frost May 11
143 growing days
First Fall Frost October 1

Prairie 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 (16 days to spare)
Start indoors: Mar 3 Transplant: May 26 🍅 Harvest: Jul 28 – Sep 8
Recommended (50%) ✓ Fits season (17 days to spare)
Start indoors: Mar 9 Transplant: Jun 1 🍅 Harvest: Aug 3 – Sep 14
Safe Start (90%) ✓ Fits season (16 days to spare)
Start indoors: Mar 21 Transplant: Jun 13 🍅 Harvest: Aug 15 – Sep 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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.7″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 531 gal / 100 sq ft
Drought risk

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

Fennel needs ~806 GDD — county provides 1,537 GDD Excellent fit

Fennel Planting Timeline โ€” Prairie County, MT

Fennel Planting Calendar

Activity When Date Range
Start Indoors March 9 Mar 9 โ€“ Mar 23
Transplant Outdoors June 1 Jun 1 โ€“ Jun 15
Direct Sow May 25 May 25 โ€“ Jun 15
Harvest August 3 Aug 3 โ€“ Sep 14

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

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March Start Indoors
April โ€”
May Direct Sow
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

143 days

Growing Tips for Prairie 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

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Frequently Asked Questions

When should I plant Fennel in Prairie County, MT?

Prairie County is in Zone 4a with an average last frost of May 11. Plan your Fennel planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Prairie County, MT?

Prairie County, Montana is in USDA Hardiness Zone 4a. The average last spring frost is May 11 and first fall frost is October 1.

๐ŸŒฑ

Plan Your Garden with Confidence

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

Get Your Free Garden Planner →

Free download. Plan your entire garden season in minutes.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Prairie County, MT. Local conditions may vary. Last updated: April 2026.