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When to Plant Fennel (herb) in Bayfield County, WI

Bayfield County, Wisconsin Zone 4b May

Top priorities for Bayfield County, Wisconsin gardeners in May

May is a pivotal month for Bayfield County, Wisconsin gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost May 14
Avg. first frost October 3
Soil temp (4") 51°F
Watering Low
Pest pressure Low
Daylight 14.8 hrs
  1. Time to transplant fennel (herb)

    Your last frost (May 14) has passed. These warm-season crops can handle outdoor soil now.

  2. Plant fennel (herb) from seed, right in the garden

    Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.

Coming up in June — start thinking about
  • Starting indoors: 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.

Bayfield County, Wisconsin is in USDA Zone 4b. The average last spring frost is May 14 and the first fall frost is October 3, giving you a growing season of approximately 142 days.

At an elevation of 619 feet, Bayfield County receives approximately 36.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 80°F, so choose short-season varieties of Fennel (herb) to ensure they mature before fall.

Bayfield County, WI (Zone 4b) Short season
142 days
Last Spring Frost May 14
142 growing days
First Fall Frost October 3
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Bayfield County Soil Profile

Soil Type

Silt Loam

Soil pH

5.8-6.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (14 days to spare)
Start indoors: Mar 26 Transplant: Apr 30 🍅 Harvest: Jul 2 – Sep 10
Recommended (50%) ✓ Fits season (16 days to spare)
Start indoors: Apr 2 Transplant: May 7 🍅 Harvest: Jul 9 – Sep 17
Safe Start (90%) ✓ Fits season (16 days to spare)
Start indoors: Apr 20 Transplant: May 25 🍅 Harvest: Jul 27 – Oct 5

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 Bayfield County

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

Soil pH

Your soil pH (5.8–6.8) is within Fennel (herb)'s preferred range (5.5–7.0).

Soil Texture

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

Organic Matter

Organic matter is excellent (4.2%) — Fennel (herb) will thrive.

How to Plant Fennel (herb)

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

Fall planting: Sow 12 weeks before your first frost date for a fall harvest.

Succession Planting Fennel (herb)

2
successive plantings in your 142-day season

Sow every 6.9 weeks. Last sowing by Jul 05 to harvest before frost.

For a dedicated fall crop, sow by Jul 11.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.1″/week
Watering frequency Natural rainfall sufficient
Season total 0 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 1.3" 0" ❄️ Dormant
Feb 1.4" 0" ❄️ Dormant
Mar 2.4" 0" ❄️ Dormant
Apr 3.8" 0" ❄️ Dormant
May 4.3" 4.4" 0" ✅ Rainfall sufficient
Jun 4.3" 4.7" 0" ✅ Rainfall sufficient
Jul 4.3" 4.4" 0" ✅ Rainfall sufficient
Aug 4.3" 3.4" 0.9" 💧 Light watering
Sep 4.3" 3.2" 1.1" 💧 Light watering
Oct 4.3" 3.1" 1.2" 💧 Light watering
Nov 2.7" 0" ❄️ Dormant
Dec 1.9" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Bayfield 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 ~750 GDD — county provides 1,420 GDD Excellent fit

Fennel (herb) Planting Timeline — Bayfield County, WI

Fennel (herb) Planting Calendar

Activity When Date Range
Start Indoors April 2 Apr 2 – Apr 16
Transplant Outdoors May 7 May 7 – May 21
Direct Sow May 7 May 7 – May 28
Harvest July 9 Jul 9 – Sep 17
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 Start Indoors
May Transplant Outdoors Direct Sow
June
July Fall Sowing Harvest
August Harvest
September Harvest
October
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 5.5–7 · Your soil: ideal

🗺️ USDA Zone

Zone 4b

📆 Growing Season

142 days in Bayfield County

Growing Tips for Fennel (herb) in Bayfield County

Direct sow Fennel (herb) outdoors after May 14 in Bayfield County when soil has warmed and frost danger has passed.

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.

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 Bayfield County, WI?

Bayfield County is in Zone 4b with an average last frost of May 14. Plan your Fennel (herb) planting based on this frost date — see the calendar above for exact timing.

What planting zone is Bayfield County, WI?

Bayfield County, Wisconsin is in USDA Hardiness Zone 4b. The average last spring frost is May 14 and first fall frost is October 3.

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Your Bayfield County Garden Planner — Free

A 24-page printable planner built for Bayfield County (Zone 4b). 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 Bayfield County, WI. Local conditions may vary. Last updated: May 2026.

Sources & credits

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