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When to Plant Onion in Hubbard County, MN

Hubbard County, Minnesota Zone 3b May

This month in Hubbard County, Minnesota

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

Avg. last frost May 12
Avg. first frost September 27
Soil temp (4") 51°F
Watering Low
Pest pressure Low
Daylight 14.9 hrs
  1. Harden off and plant onion

    Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.

  2. Scatter onion into prepared beds

    Your soil is 51°F — warm enough for these to germinate without babying.

Get ahead of June
  • Starting indoors: onion

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Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.

Hubbard County, Minnesota is in USDA Zone 3b. The average last spring frost is May 12 and the first fall frost is September 27, giving you a growing season of approximately 138 days.

At an elevation of 733 feet, Hubbard County receives approximately 32.8 inches of rainfall annually with predominantly silt loam soil. Summer highs average 79°F, so choose short-season varieties of Onion to ensure they mature before fall.

Hubbard County, MN (Zone 3b) Short season
138 days
Last Spring Frost May 12
138 growing days
First Fall Frost September 27

Hubbard County Soil Profile

Soil Type

Silt Loam

Soil pH

5.7-6.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (9 days to spare)
Start indoors: Mar 26 Transplant: May 7 🍅 Harvest: Aug 6 – Sep 10
Recommended (50%) ✓ Fits season (12 days to spare)
Start indoors: Mar 31 Transplant: May 12 🍅 Harvest: Aug 11 – Sep 15
Safe Start (90%) ✓ Fits season (14 days to spare)
Start indoors: Apr 10 Transplant: May 22 🍅 Harvest: Aug 21 – 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 Hubbard County

How your county's soil matches Onion's growing requirements.

Soil pH

Your soil pH (5.7–6.8) overlaps with Onion's range (6.0–7.0), though not a perfect match.

Soil Texture

The silt loam soil in Hubbard County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (5.2%) — Onion will thrive.

How to Plant Onion

1"
Planting Depth
6"
Between Plants
12"
Between Rows

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

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.0″/week
Watering frequency Only during dry spells
Season total 3 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Onion

Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Onion Needs Rainfall You Supplement Action
Jan 1.1" 0" ❄️ Dormant
Feb 1.4" 0" ❄️ Dormant
Mar 2.3" 0" ❄️ Dormant
Apr 3" 0" ❄️ Dormant
May 4.3" 3.8" 0.5" 💧 Light watering
Jun 4.3" 4.2" 0.1" 💧 Light watering
Jul 4.3" 3.9" 0.4" 💧 Light watering
Aug 4.3" 3.6" 0.7" 💧 Light watering
Sep 4.3" 3.2" 1.1" 💧 Light watering
Oct 2.2" 0" ❄️ Dormant
Nov 2.3" 0" ❄️ Dormant
Dec 1.7" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Hubbard County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Onion 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.

Onion needs ~971 GDD — county provides 1,276 GDD Excellent fit

Onion Planting Timeline — Hubbard County, MN

Onion Planting Calendar

Activity When Date Range
Start Indoors March 31 Mar 31 – Apr 14
Transplant Outdoors May 12 May 12 – May 26
Direct Sow May 5 May 5 – May 26
Harvest August 11 Aug 11 – Sep 15
Fall Sowing July 5 Jul 5 – Jul 19

Plant 1" deep · 6" apart · Rows 12" 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
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Only during dry spells

📅 Days to Maturity

90–120 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 3b

📆 Growing Season

138 days in Hubbard County

Growing Tips for Onion in Hubbard County

Direct sow Onion outdoors after May 12 in Hubbard County when soil has warmed and frost danger has passed.

Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.

General growing tips

Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.

Companion Planting

Good Companions

Avoid Planting Near

  • Peas
  • Green Beans
  • Asparagus

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Onion in Hubbard County, MN?

Hubbard County is in Zone 3b with an average last frost of May 12. Plan your Onion planting based on this frost date — see the calendar above for exact timing.

What planting zone is Hubbard County, MN?

Hubbard County, Minnesota is in USDA Hardiness Zone 3b. The average last spring frost is May 12 and first fall frost is September 27.

🌱

Your Hubbard County Garden Planner — Free

A 24-page printable planner built for Hubbard County (Zone 3b). 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 Hubbard County, MN. 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.