When to plant onions in Zone 4

In Zone 4, the last spring frost usually passes around May 10 and the first fall frost arrives around September 21, leaving about 134 frost-free days. The windows below are computed from those frost dates, with the same math the Dibble app uses.

Cool climate with a brief warm window. Indoor starts and season extension help.

Planting windows for onions in Zone 4

The harvest estimate counts 100 days to maturity, then a picking window of about 14 days. These windows use typical frost dates for Zone 4; Dibble pins them to your exact ZIP code.

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Onion in a Zone 4 season

Zone 4 gives about 134 frost-free days. Onion needs roughly 100 days from transplant. That leaves about 34 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 4? Pick your zone for the same dated windows.

Keep exploring

Onion: the full growing guide · The Zone 4 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.