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When to Plant Borage in Mahnomen County, MN

Borage is a self-seeding annual herb with star-shaped blue flowers that attract pollinators. Its leaves have a cucumber-like flavor and the flowers are edible.

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 Borage 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 (39 days to spare)
Start indoors: Mar 26 Transplant: Apr 30 🍅 Harvest: Jun 25 – Aug 13
Recommended (50%) ✓ Fits season (39 days to spare)
Start indoors: Apr 1 Transplant: May 6 🍅 Harvest: Jul 1 – Aug 19
Safe Start (90%) ✓ Fits season (46 days to spare)
Start indoors: Apr 11 Transplant: May 16 🍅 Harvest: Jul 11 – Aug 29

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
0.5″/week
Rainfall provides
1.0″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Borage needs ~550 GDD — county provides 1,370 GDD Excellent fit

Borage Planting Timeline โ€” Mahnomen County, MN

Borage Planting Calendar

Activity When Date Range
Start Indoors April 1 Apr 1 โ€“ Apr 15
Transplant Outdoors May 6 May 6 โ€“ May 20
Direct Sow May 6 May 6 โ€“ May 27
Fall Sowing July 5 Jul 5 โ€“ Jul 19
Harvest July 1 Jul 1 โ€“ Aug 19

Plant 0.5" deep ยท 8" apart ยท Rows 12" 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 โ€”
October โ€”
November โ€”
December โ€”

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Low โ€” drought tolerant

Days to Maturity

50โ€“60 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 3b

Growing Season

137 days

Growing Tips for Mahnomen County

Direct sow in spring as borage does not transplant well. Allow some plants to go to seed for next year. Young leaves are best; older leaves become bristly.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Borage in Mahnomen County, MN?

Mahnomen County is in Zone 3b with an average last frost of May 13. Plan your Borage 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.

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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.