Maine · zones 3b–6a
When to plant sweet potatoes in Maine.
Sow or transplant between Jun 14 to Jul 29 in a typical year, keyed to Maine's median last frost around May 8. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Sweet Potatoes dates for a typical Maine season.
1 · Start indoors
May 3 to Jun 17
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Jun 14 to Jul 29
Keyed to the ~May 8 last frost. Sow 3" deep, 14" apart.
Harvest
~110 days later
~2.5 lb per plant over ~1 weeks.
Maine spans more than one climate: Zone 5 is the most common zone, but the state runs 3b to 6a. 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.