When to plant onions in Zone 3

In Zone 3, the last spring frost usually passes around May 15 and the first fall frost arrives around September 15, leaving about 123 frost-free days. The windows below are computed from those frost dates, with the same math the Dibble app uses.

Short, cool season. Start most warm crops indoors and protect from late frosts.

Planting windows for onions in Zone 3

The harvest estimate counts 100 days to maturity, then a picking window of about 14 days. These windows use typical frost dates for Zone 3; Dibble pins them to your exact ZIP code.

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Onion in a Zone 3 season

Zone 3 gives about 123 frost-free days. Onion needs roughly 100 days from transplant. That leaves about 23 days of slack, enough for one full crop with a little room for a cold spring.

How to grow onions

Start onion seeds indoors 10 weeks before last frost, or use sets. Transplant 2 weeks before last frost, onions are hardy and size up with cool early growth.

Companion plants

Good neighbors for Onion:

Better kept apart:

Onion in other zones

Not in Zone 3? Pick your zone for the same dated windows.

Keep exploring

Onion: the full growing guide · The Zone 3 planting calendar · Every crop and zone

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Dates are estimates based on typical frost dates for the zone. Your yard has its own microclimate, so use them as a starting point and adjust as you learn your space.