Montana · zones 4a–5b
When to plant sweet corn in Montana.
Sow between May 22 to Aug 21 in a typical year, keyed to Montana's median last frost around May 15. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Sweet Corn dates for a typical Montana season.
Direct sow
May 22 to Aug 21
Keyed to the ~May 15 last frost. Sow 1.5" deep, 12" apart.
Harvest
~75 days later
~1 lb per plant over ~1 weeks.
Montana spans more than one climate: Zone 4 is the most common zone, but the state runs 4a to 5b. 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.