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When to Plant Fennel in Clay County, MN

Clay County, Minnesota Zone 4a May

May to-do list for Clay County, Minnesota

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Clay County, Minnesota.

Avg. last frost May 11
Avg. first frost September 30
Soil temp (4") 48°F
Watering Low
Pest pressure Low
Daylight 14.8 hrs
  1. Sow fennel where they'll grow

    Thin ruthlessly once seedlings are up. Crowded roots mean smaller crops from every plant.

Looking ahead to June
  • Transplants going out: fennel

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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.

Clay County, Minnesota is in USDA Zone 4a. The average last spring frost is May 11 and the first fall frost is September 30, giving you a growing season of approximately 142 days.

At an elevation of 1,220 feet, Clay County receives approximately 35.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 80°F, so choose short-season varieties of Fennel to ensure they mature before fall.

Clay County, MN (Zone 4a) Short season
142 days
Last Spring Frost May 11
142 growing days
First Fall Frost September 30
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Clay County Soil Profile

Soil Type

Silt Loam

Soil pH

5.9-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (19 days to spare)
Start indoors: Feb 28 Transplant: May 23 🍅 Harvest: Jul 25 – Sep 5
Recommended (50%) ✓ Fits season (16 days to spare)
Start indoors: Mar 9 Transplant: Jun 1 🍅 Harvest: Aug 3 – Sep 14
Safe Start (90%) ✓ Fits season (18 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.

Soil Compatibility in Clay County

How your county's soil matches Fennel's growing requirements.

Soil pH

Your soil pH (5.9–6.9) is within Fennel's preferred range (5.5–7.0).

Soil Texture

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

Organic Matter

Organic matter is excellent (4.6%) — Fennel will thrive.

How to Plant Fennel

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

Succession Planting Fennel

2
successive plantings in your 142-day season

Sow every 6.9 weeks. Last sowing by Jul 02 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
1.0″/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

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 1.4" 0" ❄️ Dormant
Feb 1.5" 0" ❄️ Dormant
Mar 2.8" 0" ❄️ Dormant
Apr 3.9" 0" ❄️ Dormant
May 2.6" 3.8" 0" ✅ Rainfall sufficient
Jun 2.6" 3.8" 0" ✅ Rainfall sufficient
Jul 2.6" 4.3" 0" ✅ Rainfall sufficient
Aug 2.6" 4.2" 0" ✅ Rainfall sufficient
Sep 2.6" 2.8" 0" ✅ Rainfall sufficient
Oct 2.6" 0" ❄️ Dormant
Nov 2.2" 0" ❄️ Dormant
Dec 2.2" 0" ❄️ Dormant

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

Fennel Planting Timeline — Clay County, MN

Fennel Planting Calendar

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

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.6"/week · Natural rainfall sufficient

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 5.5–7 · Your soil: ideal

🗺️ USDA Zone

Zone 4a

📆 Growing Season

142 days in Clay County

Growing Tips for Fennel in Clay County

Direct sow Fennel outdoors after May 11 in Clay 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

  • Tomatoes
  • Peppers
  • Beans

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Fennel in Clay County, MN?

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

What planting zone is Clay County, MN?

Clay County, Minnesota is in USDA Hardiness Zone 4a. The average last spring frost is May 11 and first fall frost is September 30.

🌱

Your Clay County Garden Planner — Free

A 24-page printable planner built for Clay County (Zone 4a). 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 Clay County, MN. 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.