When to Plant Onion in Minnesota

Growing Onion in Minnesota: Complete Guide

Onion (Allium cepa) is a warm-season crop that needs a head start indoors before Minnesota's last frost. Depending on your zone, Minnesota gardeners start seeds indoors between March 10, 2027 (Zone 4b) and March 30, 2027 (Zone 3a), then move transplants outside once their zone's last frost has passed — the zone table above has your exact dates.

Because Minnesota stretches across 5 USDA hardiness zones (3a, 3b, 4a, 4b, 5a), planting windows can shift by as much as six to eight weeks from one end of the state to the other. Gardeners in the warmer southern zones can start earlier, while those in cooler northern zones should wait until the zone table above shows their last frost has passed.

With 100 days to maturity, Onion needs the indoor head start that Minnesota's growing season requires. Starting indoors ensures you have strong transplants ready the moment outdoor conditions are right.

Onion requires full sun (6+ hours) and moderate moisture. Midwest growing seasons are compressed between late spring frosts and fall cold snaps, so timing transplants precisely pays off.

For the most precise planting dates tailored to your exact location, enter your ZIP code on our planting calendar or use the zone table above to find the schedule for your area of Minnesota.