Washington DC · zones 7b–7b
When to plant onions in Washington DC.
Sow or transplant between Jan 26 to Mar 11 in a typical year, keyed to Washington DC's median last frost around Apr 5. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Onions dates for a typical Washington DC season.
1 · Start indoors
Dec 15 to Jan 28
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Jan 26 to Mar 11
Keyed to the ~Apr 5 last frost. Sow 0.5" deep, 4" apart.
Harvest
~95 days later
~0.5 lb per plant over ~1 weeks.
Washington DC spans more than one climate: Zone 7 is the most common zone, but the state runs 7b to 7b. 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.