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When to plant Fennel (herb) in Gallatin County County,

Plant Fennel (herb) in Gallatin County County from May 25 to June 15 in spring. Gallatin County County sits in USDA Zone 5a, with last frost around June 8 and first frost on September 19. A second sowing from July 11 to July 25 extends the harvest into fall.

When to Plant Fennel (herb) in Gallatin County, MT

Gallatin County, Montana Zone 5a June

June to-do list for Gallatin County, Montana

Here's what deserves your attention in Gallatin County, Montana this month. Everything below is tailored to Zone 5a and timed around your local frost dates.

Avg. last frost June 8
Avg. first frost September 19
Soil temp (4") 37°F
Watering Critical
Pest pressure High
Daylight 15.5 hrs
  1. Time to transplant fennel (herb)

    Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.

Coming up in July — start thinking about
  • Starting indoors: fennel (herb)
  • Fall sowing: fennel (herb)

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Herb fennel is grown for its aromatic leaves, stalks, and seeds rather than a bulb. It has a strong anise flavor and its flowers attract beneficial insects.

Gallatin County, Montana is in USDA Zone 5a. The average last spring frost is June 8 and the first fall frost is September 19, giving you a growing season of approximately 103 days.

At an elevation of 8,376 feet, Gallatin County receives approximately 12.4 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Fennel (herb) to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Fennel (herb) successfully. Mulch heavily to conserve soil moisture.

Gallatin County, MT (Zone 5a) Short season
103 days
Last Spring Frost June 8
103 growing days
First Fall Frost September 19

Gallatin County Soil Profile

Soil Type

Loam

Soil pH

6.2-8.1

Drainage

Well Drained

Fennel (herb) Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 20 Transplant: May 18 🍅 Harvest: Jul 20 – Sep 28
Recommended (50%) ✗ May not fit
Start indoors: May 4 Transplant: Jun 1 🍅 Harvest: Aug 3 – Oct 12
Safe Start (90%) ✗ May not fit
Start indoors: May 16 Transplant: Jun 13 🍅 Harvest: Aug 15 – Oct 24

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 Gallatin County

How your county's soil matches Fennel (herb)'s growing requirements.

Soil pH

Your soil pH (6.2–8.1) is more alkaline than Fennel (herb) prefers (5.5–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Gallatin County is excellent for Fennel (herb) — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.4%). Annual compost additions will help Fennel (herb).

How to Plant Fennel (herb)

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Fennel (herb) Water Budget

Plant needs
1.0″/week
Rainfall provides
0.5″/week
You supply
0.6″/week
Watering frequency 1-2 times/week
Season total 544 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Fennel (herb)

Fennel (herb) needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Fennel (herb) Needs Rainfall You Supplement Action
Jan 0.8" 0" ❄️ Dormant
Feb 0.8" 0" ❄️ Dormant
Mar 1.1" 0" ❄️ Dormant
Apr 1.3" 0" ❄️ Dormant
May 1.3" 0" ❄️ Dormant
Jun 4.3" 0.8" 3.5" 🚿 Regular watering
Jul 4.3" 1" 3.3" 🚿 Regular watering
Aug 4.3" 1.5" 2.8" 🚿 Regular watering
Sep 4.3" 1" 3.3" 🚿 Regular watering
Oct 1.1" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 0.8" 0" ❄️ Dormant

Water needs are for active growing months only (Jun–Sep in Gallatin County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Fennel (herb) 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 (herb) needs ~862 GDD — county provides 1,184 GDD Excellent fit

Fennel (herb) Planting Timeline — Gallatin County, MT

Fennel (herb) Planting Calendar

Activity When Date Range
Start Indoors May 4 May 4 – May 18
Transplant Outdoors June 1 Jun 1 – Jun 15
Direct Sow May 25 May 25 – Jun 15
Harvest August 3 Aug 3 – Oct 12
Fall Sowing July 11 Jul 11 – Jul 25

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 5.5–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 5a

📆 Growing Season

103 days in Gallatin County

Growing Tips for Fennel (herb) in Gallatin County

Direct sow Fennel (herb) outdoors after June 08 in Gallatin County when soil has warmed and frost danger has passed.

Your 103.0-day growing season in Gallatin County is tight for Fennel (herb) (60.0-90.0 days to maturity). Start indoors and choose early-maturing varieties.

Common pests for Fennel (herb) in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.

Gallatin County receives only 12" of rain annually. Fennel (herb) needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Direct sow in spring or fall. Unlike Florence fennel, herb fennel does not form a bulb. Harvest fronds as needed and seeds when they turn brown. Self-sows readily.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes
  • Peppers
  • Green Beans

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Fennel (herb) in Gallatin County, MT?

Gallatin County is in Zone 5a with an average last frost of June 8. Plan your Fennel (herb) planting based on this frost date — see the calendar above for exact timing.

What planting zone is Gallatin County, MT?

Gallatin County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is June 8 and first fall frost is September 19.

When should I plant Fennel (herb) in Gallatin County County, ?

In Gallatin County County, , plant Fennel (herb) after the last frost (around June 8) and before the first frost (around September 19). Best results when soil holds above 50°F.

What growing zone is Gallatin County County, for Fennel (herb)?

Gallatin County County sits in USDA Zone 5a. Fennel (herb) grows reliably in zones 4a through 10b, so it's a good fit here.

Can Fennel (herb) grow in Gallatin County County's climate?

Yes — Fennel (herb) grows well in Gallatin County County's temperate climate. Gallatin County County averages a 103-day frost-free season, with last frost around June 8 and first frost around September 19.

🌱

Your Gallatin County Garden Planner — Free

A 22-page printable planner built for Gallatin County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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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 Gallatin County, MT. Local conditions may vary. Last updated: June 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.