When to plant sweet potato in zone 4b — planting calendar

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Showing USDA Zone 4B

Growing SeasonZone 4b

Last frost ~May 15First frost ~Sep 25Today

Start indoorsTransplant / sowHarvestFrost risk

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Transplant Jun 5 · First harvest Sep 3 · Wrap by Sep 18

Last spring frostMay 15

Transplant outJun 5

First harvestSep 3

Last harvestSep 18

First fall frostSep 25

Why these dates work in zone 4b

Zone 4b's last spring frost averages May 15 and first fall frost Sep 25 — about 133 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 4b?

Sweet Potato matures in about 90–120 days from transplanting. In zone 4b that means setting plants out around Jun 5 and first picking around Sep 3.

Will sweet potato survive frost in zone 4b?

No — sweet potato is frost-sensitive. In zone 4b, wait until after the last frost (around May 15) to plant, and harvest before the first fall frost (around Sep 25).

For soil, spacing, pests and companion planting, see the full sweet potato growing guide →