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When to Plant Fennel (herb) in Griggs County, ND

Griggs County, North Dakota Zone 4a April

April in the garden — Griggs County, North Dakota

April rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Griggs County, North Dakota.

Avg. last frost May 11
Avg. first frost September 30
Soil temp (4") 40°F
Watering High
Pest pressure Low
Daylight 13.4 hrs
Looking ahead to May
  • Transplants going out: fennel (herb)
  • Direct-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.

Griggs County, North Dakota 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 660 feet, Griggs County receives approximately 21.4 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Fennel (herb) to ensure they mature before fall.

Griggs County, ND (Zone 4a) Short season
142 days
Last Spring Frost May 11
142 growing days
First Fall Frost September 30
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Griggs 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 (18 days to spare)
Start indoors: Mar 21 Transplant: Apr 25 🍅 Harvest: Jun 27 – Sep 5
Recommended (50%) ✓ Fits season (16 days to spare)
Start indoors: Mar 30 Transplant: May 4 🍅 Harvest: Jul 6 – Sep 14
Safe Start (90%) ✓ Fits season (19 days to spare)
Start indoors: Apr 10 Transplant: May 15 🍅 Harvest: Jul 17 – Sep 25

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 Griggs County

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

Soil pH

Your soil pH (6.7–7.8) 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 Griggs County is excellent for Fennel (herb) — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (3.8%). Annual compost additions will help Fennel (herb).

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 02 to harvest before frost.

For a dedicated fall crop, sow by Jul 08.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.6″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 557 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 0.6" 0" ❄️ Dormant
Feb 0.7" 0" ❄️ Dormant
Mar 1.5" 0" ❄️ Dormant
Apr 2.2" 0" ❄️ Dormant
May 4.3" 3" 1.3" 💧 Light watering
Jun 4.3" 3.5" 0.8" 💧 Light watering
Jul 4.3" 2.7" 1.6" 💧 Light watering
Aug 4.3" 2.4" 1.9" 💧 Light watering
Sep 4.3" 2" 2.3" 🚿 Regular watering
Oct 1.4" 0" ❄️ Dormant
Nov 0.7" 0" ❄️ Dormant
Dec 0.6" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Griggs 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 ~806 GDD — county provides 1,526 GDD Excellent fit

Fennel (herb) Planting Timeline — Griggs County, ND

Fennel (herb) Planting Calendar

Activity When Date Range
Start Indoors March 30 Mar 30 – Apr 13
Transplant Outdoors May 4 May 4 – May 18
Direct Sow May 4 May 4 – May 25
Harvest July 6 Jul 6 – Sep 14
Fall Sowing July 8 Jul 8 – Jul 22

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

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
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 · 1-2 times/week

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 5.5–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 4a

📆 Growing Season

142 days in Griggs County

Growing Tips for Fennel (herb) in Griggs County

Direct sow Fennel (herb) outdoors after May 11 in Griggs 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.

Griggs County receives only 21" 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 Griggs County, ND?

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

What planting zone is Griggs County, ND?

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

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Your Griggs County Garden Planner — Free

A 24-page printable planner built for Griggs 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 Griggs County, ND. Local conditions may vary. Last updated: April 2026.

Sources & credits

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