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When to Plant Borage in Pennington 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.

Pennington County, Minnesota is in USDA Zone 3b. The average last spring frost is May 10 and the first fall frost is September 30, giving you a growing season of approximately 143 days.

At an elevation of 854 feet, Pennington County receives approximately 35.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 81ยฐF, so choose short-season varieties of Borage to ensure they mature before fall.

Pennington County, MN (Zone 3b) Short season
143 days
Last Spring Frost May 10
143 growing days
First Fall Frost September 30

Pennington County Soil Profile

Soil Type

Silt Loam

Soil pH

5.9-7.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (47 days to spare)
Start indoors: Mar 21 Transplant: Apr 25 🍅 Harvest: Jun 20 – Aug 8
Recommended (50%) ✓ Fits season (45 days to spare)
Start indoors: Mar 29 Transplant: May 3 🍅 Harvest: Jun 28 – Aug 16
Safe Start (90%) ✓ Fits season (47 days to spare)
Start indoors: Apr 10 Transplant: May 15 🍅 Harvest: Jul 10 – Aug 28

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 ~591 GDD — county provides 1,537 GDD Excellent fit

Borage Planting Timeline โ€” Pennington County, MN

Borage Planting Calendar

Activity When Date Range
Start Indoors March 29 Mar 29 โ€“ Apr 12
Transplant Outdoors May 3 May 3 โ€“ May 17
Direct Sow May 3 May 3 โ€“ May 24
Fall Sowing July 8 Jul 8 โ€“ Jul 22
Harvest June 28 Jun 28 โ€“ Aug 16

Plant 0.5" deep ยท 8" apart ยท Rows 12" apart

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March Start Indoors
April Start Indoors
May Transplant Outdoors Direct Sow
June Harvest
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

143 days

Growing Tips for Pennington 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 Pennington County, MN?

Pennington County is in Zone 3b with an average last frost of May 10. Plan your Borage planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Pennington County, MN?

Pennington County, Minnesota is in USDA Hardiness Zone 3b. The average last spring frost is May 10 and first fall frost is September 30.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Pennington 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 Pennington County, MN. Local conditions may vary. Last updated: April 2026.