Last spring frostMay 7
Transplant outMay 28
First harvestAug 26
Last harvestSep 16
First fall frostOct 13
Why these dates work in zone 4a
Zone 4a's last spring frost averages May 7 and first fall frost Oct 13 — about 159 frost-free days. Sweet Potato is frost-sensitive, so the 3w after frost timing builds in a safety margin against a late cold snap — setting plants out too early risks losing them to frost.
Common questions
How long does sweet potato take to grow in zone 4a?
Sweet Potato matures in about 90–120 days from transplanting. In zone 4a that means setting plants out around May 28 and first picking around Aug 26.
Will sweet potato survive frost in zone 4a?
No — sweet potato is frost-sensitive. In zone 4a, wait until after the last frost (around May 7) to plant, and harvest before the first fall frost (around Oct 13).
For soil, spacing, pests and companion planting, see the full sweet potato growing guide →