Alaska · zones 3a–8a
When to plant onions in Alaska.
Sow or transplant between Mar 4 to Apr 17 in a typical year, keyed to Alaska's median last frost around May 12. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Onions dates for a typical Alaska season.
1 · Start indoors
Jan 21 to Mar 6
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Mar 4 to Apr 17
Keyed to the ~May 12 last frost. Sow 0.5" deep, 4" apart.
Harvest
~95 days later
~0.5 lb per plant over ~1 weeks.
Alaska spans more than one climate: Zone 3 is the most common zone, but the state runs 3a to 8a. That's why the planner works from your ZIP code's frost dates, not your zone — mountain and coastal gardens in the same state can be three weeks apart.