South Dakota · zones 4a–5a
When to plant sweet corn in South Dakota.
Sow between May 16 to Aug 15 in a typical year, keyed to South Dakota's median last frost around May 9. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Sweet Corn dates for a typical South Dakota season.
Direct sow
May 16 to Aug 15
Keyed to the ~May 9 last frost. Sow 1.5" deep, 12" apart.
Harvest
~75 days later
~1 lb per plant over ~1 weeks.
South Dakota spans more than one climate: Zone 4 is the most common zone, but the state runs 4a to 5a. 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.