When to plant onions in Zone 10

In Zone 10, the last spring frost usually passes around January 31 and the first fall frost arrives around December 15, leaving about 318 frost-free days. The windows below are computed from those frost dates, with the same math the Dibble app uses.

Nearly frost-free. Grow cool crops in winter; summers are too hot for many vegetables.

Planting windows for onions in Zone 10

The harvest estimate counts 100 days to maturity, then a picking window of about 14 days. These windows use typical frost dates for Zone 10; Dibble pins them to your exact ZIP code.

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Onion in a Zone 10 season

Zone 10 gives about 318 frost-free days. Onion needs roughly 100 days from transplant. That leaves about 218 days of slack, so there is room for a late start or a second planting.

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 10? Pick your zone for the same dated windows.

Keep exploring

Onion: the full growing guide · The Zone 10 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.