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When to plant basil in zone 4b

In zone 4b, where the last spring frost typically comes around May 8, start basil indoors April 9 to 23 and plant out May 28 to June 4.

The zone 4b schedule for basil

Start seeds indoors
April 9 to 23
Plant out
May 28 to June 4
Sow outdoors
May 28 to June 4
Soil warm enough (60°F), about
May 28
First harvest, roughly
June 27 to July 4

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 basil.

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

Basil 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 basil

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

Basil in zone 4b cities

CityTypical last frostStart indoorsPlant out
Rochester, MNApr 30Apr 4 to 18May 23 to 30
Duluth, MNMay 6May 3 to 17Jun 21 to 28
Lakeville, MNMay 2Apr 5 to 19May 24 to 31
St. Cloud, MNMay 7Apr 8 to 22May 27 to Jun 3
Eau Claire, WIMay 8Apr 5 to 19May 24 to 31
Great Falls, MTMay 19May 1 to 15Jun 19 to 26

How to grow basilAll zonesBasil in zone 4aBasil in zone 5aAbout zone 4b

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