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 seeds indoors about 8 weeks before planting out, or use sets. Match the variety to your day length (short-day types near the equator, long-day types far from it) and plant out in the cool part of the year. Cure the bulbs in dry weather once the tops fall over.

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.