Root Vegetable

When to Plant Onions in Michigan

The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.

The Short Answer

Michigan is solidly long-day onion territory, and the state's moderate growing season produces excellent storage onions. The sandy soils of western Michigan are naturally well-suited to onion growing, providing the loose, well-drained conditions the crop prefers.

Michigan Frost Dates

Your planting dates depend on which part of Michigan you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Upper Peninsula 4a, 4b, 5a May 15 - Jun 5 Sep 10 - Sep 25
Northern Lower Michigan 5a, 5b May 10 - May 25 Sep 20 - Oct 5
Southern Michigan 5b, 6a, 6b Apr 25 - May 10 Oct 1 - Oct 15

Onions Planting Schedule for Michigan

Upper Peninsula (Zones 4a, 4b, 5a)

Average last frost: May 15 - Jun 5 · Average first frost: Sep 10 - Sep 25

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Northern Lower Michigan (Zones 5a, 5b)

Average last frost: May 10 - May 25 · Average first frost: Sep 20 - Oct 5

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Southern Michigan (Zones 5b, 6a, 6b)

Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15

Start Seeds Indoors
10 wks before frost
Transplant Outside
4 wks before frost
Direct Sow
4 wks before frost

Growing Onions in Michigan

State-Specific Growing Tips

Plant sets or transplants from mid-April when soil can be worked. For the largest bulbs, start seed indoors 10-12 weeks before last frost. Long-day onions bulb when days exceed 14-16 hours — this occurs in late June in Michigan. The bulbing period is the critical growth phase — ensure consistent moisture and fertility. Cure in a warm, dry location for 2-3 weeks before storage. Sandy western Michigan soils are ideal for onions.

Recommended Varieties for Michigan

Long-day only: Copra (best storage), Walla Walla (sweet, eat fresh), Yellow Globe Danvers, Redwing (red storage). MSU Extension recommends starting with sets for beginners and transplants for larger bulbs.

Common Challenges in Michigan

Onion maggot. Thrips. Neck rot during wet conditions. Downy mildew in humid summers. Botrytis leaf blight.

Growing Tips

Day length triggers bulbing. Northern gardeners need long-day varieties. Southern gardeners need short-day varieties.

Companion Planting

Plant onions alongside these companions for better growth:

Carrots Lettuce Beets Tomatoes

Keep onions away from:

Beans Peas

The Bottom Line

Onions can be grown successfully in Michigan with proper attention to regional frost dates and local growing conditions. Timing varies across the state — Upper Peninsula gardeners work with a last frost around May 15 - Jun 5, while Southern Michigan sees frost end around Apr 25 - May 10. Choose varieties suited to your region, amend your soil based on its specific needs, and monitor for the pests and diseases most common in your area. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Onions Growing Guide National planting guide with all states Michigan Planting Calendar All plants for Michigan Onions in Alabama Alabama planting dates Onions in Alaska Alaska planting dates Onions in Arizona Arizona planting dates Onions in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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