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When to Plant Cauliflower in Mahnomen County, MN

Cauliflower is a cool-season brassica that produces dense white, purple, or green heads called curds. It is more finicky than broccoli but rewards with a mild, nutty flavor.

Mahnomen County, Minnesota is in USDA Zone 3b. The average last spring frost is May 13 and the first fall frost is September 27, giving you a growing season of approximately 137 days.

At an elevation of 1,223 feet, Mahnomen County receives approximately 33.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 80ยฐF, so choose short-season varieties of Cauliflower to ensure they mature before fall.

Mahnomen County, MN (Zone 3b) Short season
137 days
Last Spring Frost May 13
137 growing days
First Fall Frost September 27

Mahnomen County Soil Profile

Soil Type

Silt Loam

Soil pH

5.9-7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (18 days to spare)
Start indoors: Mar 26 Transplant: May 7 🍅 Harvest: Jul 2 – Sep 3
Recommended (50%) ✓ Fits season (18 days to spare)
Start indoors: Apr 1 Transplant: May 13 🍅 Harvest: Jul 8 – Sep 9
Safe Start (90%) ✓ Fits season (25 days to spare)
Start indoors: Apr 11 Transplant: May 23 🍅 Harvest: Jul 18 – Sep 19

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.

Plant Water Budget

Plant needs
1.5″/week
Rainfall provides
1.0″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 1,140 gal / 100 sq ft
Cauliflower needs ~775 GDD — county provides 1,370 GDD Excellent fit

Cauliflower Planting Timeline โ€” Mahnomen County, MN

Cauliflower Planting Calendar

Activity When Date Range
Start Indoors April 1 Apr 1 โ€“ Apr 15
Transplant Outdoors May 13 May 13 โ€“ May 27
Direct Sow May 6 May 6 โ€“ May 27
Fall Sowing July 5 Jul 5 โ€“ Jul 19
Harvest July 8 Jul 8 โ€“ Sep 9

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

Month-by-Month Timeline

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

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

High โ€” keep soil consistently moist

Days to Maturity

55โ€“100 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 3b

Growing Season

137 days

Growing Tips for Mahnomen County

Start seeds indoors 6 weeks before transplanting. Blanch white varieties by tying outer leaves over the head. Provide consistent moisture and avoid temperature extremes.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes
  • Strawberries

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Frequently Asked Questions

When should I plant Cauliflower in Mahnomen County, MN?

Mahnomen County is in Zone 3b with an average last frost of May 13. Plan your Cauliflower planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Mahnomen County, MN?

Mahnomen County, Minnesota is in USDA Hardiness Zone 3b. The average last spring frost is May 13 and first fall frost is September 27.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Mahnomen County gardeners in Zone 3b organize planting dates, track what's growing, and never miss a planting window.

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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 Mahnomen County, MN. Local conditions may vary. Last updated: April 2026.