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When to plant onions in zone 3b

In zone 3b, where the last spring frost typically comes around May 17, start onions indoors January 25 to March 8 and plant out April 19 to May 3.

The zone 3b schedule for onions

Start seeds indoors
January 25 to March 8
Plant out
April 19 to May 3
Sow outdoors
April 5 to 19

From the median frost dates of the NOAA stations assigned to the 200 ZIP codes in zone 3b, and the timing recommended by Cooperative Extension guides for onions.

Dates before the last frost assume the soil has thawed and is dry enough to work: a squeezed handful crumbles instead of sticking. After a late or wet spring, wait for that even if the date has passed.

Frost risk in zone 3b

Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 3b, the typical last frost ranges from about May 12 in the earliest tenth of ZIP codes to May 29 in the latest tenth, and the first fall frost from September 13 to October 1. For a typical place in the zone:

  • May 4Risky: a later frost happens in 9 years out of 10
  • May 17Typical: frost after this date in half of years
  • May 30Safe: a later frost only 1 year in 10

Your dates for onions

Set your ZIP code at the top of the page and we will work out when to plant onions where you live, from the frost records of the nearest NOAA weather station. Your ZIP code is remembered on this device only.

Enter your ZIP code

How to grow onionsAll zonesOnions in zone 3aOnions in zone 4aAbout zone 3b

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