Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production
Several areas of Minnesota, including areas around Alexandria, Brainerd, and Grand Rapids may experience below-freezing temperatures tonight and potentially tomorrow night.
The temperatures in the weather forecast will not necessarily reflect the temperatures in a berry field, as temperatures can be lower at ground level. Therefore, having a weather station or basic thermometers out in the field will help accurately monitor temperatures and determine the need to implement freeze protection measures.
Critical freeze temperatures:
- Blueberries at full bloom: 28 degrees F
- Blueberries at petal fall: 30 degrees F
- Strawberries at full bloom: 30 degrees F
- Strawberries at "popcorn" stage (not fully opened, but petals visible): 26 degrees F
Options:
The two options for freeze protection for berry crops are overhead irrigation and row covers. Running drip irrigation overnight will not protect berries. If using overhead irrigation, it has be be continually run from the time the temperature dips below 32F, until temperatures raise back up and the water melts off of the plants. The rate of water flow (gallons per minute) depends on temperature and wind speed.
Reading materials:
Using Sprinklers to Protect Blueberries from Spring Freeze - Michigan State University
Irrigation for Frost Protection of Strawberries - OMAFRA
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