Missouri · zones 5b–7a
When to plant onions in Missouri.
Sow or transplant between Feb 5 to Mar 21 in a typical year, keyed to Missouri's median last frost around Apr 15. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Onions dates for a typical Missouri season.
1 · Start indoors
Dec 25 to Feb 7
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Feb 5 to Mar 21
Keyed to the ~Apr 15 last frost. Sow 0.5" deep, 4" apart.
Harvest
~95 days later
~0.5 lb per plant over ~1 weeks.
Missouri spans more than one climate: Zone 6 is the most common zone, but the state runs 5b to 7a. 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.