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When to plant sweet potatoes in zone 4a

In zone 4a, where the last spring frost typically comes around May 13, plant out June 19 to 26.

The zone 4a schedule for sweet potatoes

Plant out
June 19 to 26
Soil warm enough (65°F), about
June 19
First harvest, roughly
September 17 to October 24

From the median frost dates of the NOAA stations assigned to the 739 ZIP codes in zone 4a, and the timing recommended by Cooperative Extension guides for sweet potatoes.

Frost risk in zone 4a

Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 4a, the typical last frost ranges from about May 6 in the earliest tenth of ZIP codes to May 24 in the latest tenth, and the first fall frost from September 20 to October 3. For a typical place in the zone:

  • April 30Risky: a later frost happens in 9 years out of 10
  • May 13Typical: frost after this date in half of years
  • May 27Safe: a later frost only 1 year in 10

Sweet Potatoes are killed by frost, so if you want to be safe, plant out after the safe date rather than the typical one, or be ready to cover plants on a cold night.

Your dates for sweet potatoes

Set your ZIP code at the top of the page and we will work out when to plant sweet potatoes where you live, from the frost records of the nearest NOAA weather station. Your ZIP code is remembered on this device only.

Enter your ZIP code

Sweet Potatoes in zone 4a cities

CityTypical last frostPlantFall
Fargo, NDMay 10Jun 8 to 15—
Bismarck, NDMay 14Jun 14 to 21—
Grand Forks, NDMay 10Jun 13 to 20—

How to grow sweet potatoesAll zonesSweet Potatoes in zone 3bSweet Potatoes in zone 4bAbout zone 4a

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