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When to Plant Brussels Sprouts in Griggs County, ND

Griggs County, North Dakota Zone 4a May

This month in Griggs County, North Dakota

Your garden in Griggs County, North Dakota is working on a schedule, even when you're not. Here's where you should be this May.

Avg. last frost May 11
Avg. first frost September 30
Soil temp (4") 53°F
Watering Moderate
Pest pressure Low
Daylight 14.9 hrs
  1. Get brussels sprouts in the ground

    Frost risk is low now in Griggs County, North Dakota. If you've been covering beds overnight, you can stop.

  2. Direct-sow brussels sprouts

    Keep the top inch of soil moist until germination — a gentle morning watering for 5–7 days does the job.

June prep starts now
  • Starting indoors: brussels sprouts

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Brussels sprouts are a cold-hardy brassica that produces miniature cabbage-like heads along a tall stalk. Flavor improves after a light frost.

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 Brussels Sprouts 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) ✗ May not fit
Start indoors: Mar 21 Transplant: May 2 🍅 Harvest: Aug 1 – Sep 26
Recommended (50%) ✗ May not fit
Start indoors: Mar 30 Transplant: May 11 🍅 Harvest: Aug 10 – Oct 5
Safe Start (90%) ✗ May not fit
Start indoors: Apr 10 Transplant: May 22 🍅 Harvest: Aug 21 – Oct 16

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 Brussels Sprouts's growing requirements.

Soil pH

Your soil pH (6.7–7.8) overlaps with Brussels Sprouts's range (6.0–7.5), though not a perfect match.

Soil Texture

The loam soil in Griggs County is excellent for Brussels Sprouts — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (3.8%). Annual compost additions will help Brussels Sprouts.

How to Plant Brussels Sprouts

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

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

Plant Water Budget

Plant needs
0.9″/week
Rainfall provides
0.6″/week
You supply
0.3″/week
Watering frequency 1-2 times/week
Season total 405 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Brussels Sprouts

Brussels Sprouts needs approximately 0.9 inches of water per week (3.9" per month). Here's how your county's rainfall compares month by month.

Month Brussels Sprouts 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 3.9" 3" 0.9" 💧 Light watering
Jun 3.9" 3.5" 0.4" 💧 Light watering
Jul 3.9" 2.7" 1.2" 💧 Light watering
Aug 3.9" 2.4" 1.5" 💧 Light watering
Sep 3.9" 2" 1.9" 💧 Light 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.

Brussels Sprouts 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.

Brussels Sprouts needs ~1,182 GDD — county provides 1,526 GDD Good fit

Brussels Sprouts Planting Timeline — Griggs County, ND

Brussels Sprouts Planting Calendar

Activity When Date Range
Start Indoors March 30 Mar 30 – Apr 13
Transplant Outdoors May 11 May 11 – May 25
Direct Sow May 4 May 4 – May 25
Harvest August 10 Aug 10 – Oct 5
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
August Harvest
September Harvest
October Harvest
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.9"/week · 1-2 times/week

📅 Days to Maturity

90–130 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 4a

📆 Growing Season

142 days in Griggs County

Growing Tips for Brussels Sprouts in Griggs County

Direct sow Brussels Sprouts outdoors after May 11 in Griggs County when soil has warmed and frost danger has passed.

Your 142.0-day growing season in Griggs County is tight for Brussels Sprouts (90.0-130.0 days to maturity). Start indoors and choose early-maturing varieties.

Common pests for Brussels Sprouts in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.

Griggs County receives only 21" of rain annually. Brussels Sprouts needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors 12-14 weeks before first fall frost. Stake tall plants to prevent toppling. Remove lower leaves as sprouts develop to improve air circulation.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes
  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Brussels Sprouts in Griggs County, ND?

Griggs County is in Zone 4a with an average last frost of May 11. Plan your Brussels Sprouts 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: May 2026.

Sources & credits

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