Planting Guides

When to Plant Onions in Minneapolis: Complete Guide + Best Varieties for Zone 4a

Minneapolis, Minnesota

USDA Zone 4a

Last Frost: May 15

Last updated: December 8, 2025

Learn when to plant onions in Minneapolis with specific dates for Zone 4a. Compare 6 varieties & discover which onions grow best in Minnesota's climate.

AAmanda Foster

December 8, 2025

Fresh harvested onions on wooden table with Minneapolis skyline background showing successful Zone 4a onion growing — — Image © PlantReference.org 2026

Quick Answer

Plant onions in Minneapolis April 15-30 with long-day varieties like Walla Walla. Harvest August-September after 110-125 growing days.

TL;DR

Plant onions in Minneapolis from April 15-30 using long-day varieties like Walla Walla or Red Wing. Minneapolis' Zone 4a requires varieties needing 14+ hours daylight to bulb properly. Plant garlic in mid-October for June harvest.

Frequently Asked Questions

What's the latest I can plant onions in Minneapolis?

April 30 is your absolute deadline for spring onion planting in Minneapolis. Later planting doesn't give enough time for adequate leaf development before our summer solstice triggers bulbing. I've seen people try May plantings, but they always get small bulbs that barely store through winter. The onions need those cool spring weeks to build the foliage that becomes your storage bulbs.

Can I grow short-day onions like Texas varieties in Minneapolis?

No, don't waste your time. Short-day onions need only 10-12 hours of daylight to trigger bulbing, but Minneapolis gets 15+ hours in summer. They'll stay in leaf production mode all season and never form bulbs. You might get massive green tops, but no storage onions. Stick with long-day varieties—it's the only type that works at our 45°N latitude.

Should I use onion sets, transplants, or seeds in Minneapolis?

Sets are your best bet for Minneapolis. Our growing season is only 138 days, which doesn't give enough time to start from seed unless you're growing them indoors for 8-10 weeks. Transplants work well too, but sets are more cold-tolerant and handle our unpredictable April weather better. Choose sets smaller than a dime—large ones bolt when hit by late frost followed by warm spells.

When should I plant garlic in Minneapolis, and what type works best?

Plant garlic October 10-15 in Minneapolis, about 4-6 weeks before ground freezes. Use hardneck varieties like Allium sativum 'Music' or Allium sativum 'German Extra Hardy'—they need our cold winters for proper clove development. Softneck types don't get enough chill hours here and often produce solid bulbs instead of separated cloves.

My onions formed flower stalks in June. What went wrong?

That's bolting, usually caused by planting large onion sets (bigger than a dime) or temperature stress from late cold snaps. Large sets are biologically older and think they've been through a winter when hit by cold followed by warm weather. Cut those flower stalks immediately to salvage some bulb development, but expect smaller onions that won't store well. Next year, use smaller sets and wait until soil consistently stays above 35°F.

How do I store Minneapolis-grown onions through winter?

Cure them properly first—that's the key. After harvest, dry bulbs in single layers in a warm (75-80°F (24-27°C)), dry, ventilated area for 2-4 weeks until skins are papery. Then store at 32-40°F (0-4°C) with 60-70% humidity. Most Minneapolis basements work perfectly. Don't store with potatoes, and check monthly, removing any that show soft spots. Well-cured storage varieties like Allium cepa 'Red Wing' keep until March.

Can I plant onions in fall for overwintering in Minneapolis Zone 4a?

It's risky in Minneapolis. While some gardeners succeed with heavy mulch protection, our Zone 4a winters often kill overwintering onions. The specialty overwintering varieties like Allium cepa 'Bridger' are bred for Zones 6-7 with milder winters. Stick with spring planting for reliable results, though you can try a small test patch with 6 inches (15 cm) of straw mulch if you want to experiment.

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Written By

Amanda Foster

Amanda came to gardening through an unexpected route—after developing chronic pain from rheumatoid arthritis in her late 20s, she started researching adaptive gardening techniques that would allow her to continue growing plants without aggravating her condition. Now based in Minneapolis, she writes about accessible gardening, raised bed designs for people with mobility challenges, and ergonomic tools that reduce strain. Amanda completed a certificate in sustainable urban agriculture and volunteers with a nonprofit that builds accessible community gardens. She grows vegetables, herbs, and flowers in waist-high raised beds she designed herself. Her writing focuses on practical solutions that work for real people with real limitations—whether that's arthritis, limited mobility, or just a bad back.