The official air temperature at the West Central Research and Outreach Center on October 4, 2014 was 32 degrees. Even with the air temperature at 32, the temperature recorded in the low tunnel system was 34 degrees, which prevented the day neutral strawberry flowers and fruit from frost damage. By comparison, the non low tunnel system was at 31 degrees, and exhibited frost damage to open flowers.
In order to graph hi/low temperatures throughout the season, we installed Watch Dog temperature gauges in both the low tunnel system and non low tunnel system. Gauges are placed 12 inches above the ground; however, the gauge for the low tunnel system sits above ground yet is covered by the plastic hoop.
When we first construct a low tunnel, the sides are rolled up to 20 inches and left there for the season for ventilation and harvesting purposes. When it comes to frost, the low tunnel system offers protection similar to a shade tree. Imagine a large shade tree in your yard, and there is a frost event. Underneath the tree is wet, but beyond the perimeter of the tree is white frost. Frost appears on the lawn; it does not move laterally under the tree. The low tunnel offers the same protection to day neutral strawberry plants – the frost will appear on top of the hoop, and in between the rows, but does not appear on the strawberries or flowers.