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When to plant sunflowers in zone 4b

In zone 4b, where the last spring frost typically comes around May 8, sow outdoors May 8 to 29.

The zone 4b schedule for sunflowers

Sow outdoors
May 8 to 29
Safest planting date (10% frost risk)
May 22
First harvest, roughly
June 27 to August 27

From the median frost dates of the NOAA stations assigned to the 1,164 ZIP codes in zone 4b, and the timing recommended by Cooperative Extension guides for sunflowers.

Frost risk in zone 4b

Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 4b, the typical last frost ranges from about May 1 in the earliest tenth of ZIP codes to May 25 in the latest tenth, and the first fall frost from September 22 to October 8. For a typical place in the zone:

  • April 26Risky: a later frost happens in 9 years out of 10
  • May 8Typical: frost after this date in half of years
  • May 22Safe: a later frost only 1 year in 10

Sunflowers 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 sunflowers

Set your ZIP code at the top of the page and we will work out when to plant sunflowers 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

Sunflowers in zone 4b cities

CityTypical last frostPlantFall
Rochester, MNApr 30Apr 30 to May 21—
Duluth, MNMay 6May 19 to Jun 9—
Lakeville, MNMay 2May 2 to 23—
St. Cloud, MNMay 7May 7 to 28—
Eau Claire, WIMay 8May 8 to 29—
Great Falls, MTMay 19May 19 to Jun 9—

How to grow sunflowersAll zonesSunflowers in zone 4aSunflowers in zone 5aAbout zone 4b

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