Spring Row Cover Management for Plasticulture Strawberries

Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu

Floating row covers are used to protect plasticulture strawberries during the coldest part of the winter, but as temperatures warm, row covers should be removed and reapplied only as needed for freeze protection. The highest yield potentials are usually obtained by uncovering and covering in the late winter and spring based on expected temperatures, compared to the practice of keeping strawberries continuously covered into the flowering or early fruiting stage. Leaving row cover on too long can cause strawberries to flower earlier in the season when they will be more likely to experience freeze damage. Additionally, row covers don’t permit pollinators to access flowers, resulting in poor pollination and small fruit size. Row covers may also inhibit plant growth and productivity by restricting light or raising temperatures above of the optimal range for strawberries, which is 68-75 °F during the day.

The threshold temperature at which strawberry yield will be impacted by cold depends on the flowering stage. Before flower buds emerge, temperatures down to 10 °F are tolerated without damage. Freeze susceptibility increases as buds emerge and progress towards flowering. Open flowers are the stage most susceptible to freeze injury.

Critical Temperatures for Strawberries

When weather forecasts indicate that temperatures at ground level will be below the critical temperature for the most susceptible flower stage present, row covers should be reapplied. When a freeze is predicted it is beneficial to apply row covers in the afternoon to build up heat before temperatures drop.

A single layer, medium weight floating row cover will give about 4 degrees of protection. Adding a second layer of row cover can increase protection. Kathy Demchak at Penn State reports successful frost protection with double row covers down to 21 °F.