When to mulch strawberries this fall

 

Author: Annie Klodd, University of Minnesota Extension Educator - Fruit and Vegetable Production

The point of spreading straw over strawberries in the fall is to protect them from harsh winter temperatures. Straw does not need to go on this early, but rather growers should make plans now to do it in a couple of weeks. In fact, straw application must wait until after strawberry plants go dormant for the season. Otherwise, they will be weakened by attempting to grow under the straw.

In Minnesota, dormancy usually happens sometime in November. 

 

When strawberry plants are dormant: A very general rule is to apply mulch once temperatures dip below 20 degrees F, as long as the plants have had a chance to go dormant and acclimate to late fall temperatures. A more precise rule is to wait until the soil temperature has remained at or below 40 degrees F at 4 inches depth for at least 3 consecutive days.

The presence of October snows might tempt a strawberry grower to apply straw now, but resist this urge. Since the plants were still growing before the snow, they are unlikely to be dormant now, and the soil temperatures are not low enough yet.

According to Steve Poppe, former UMN researcher and strawberry grower in western Minnesota, growers can and should still hold off on mulch application for a couple more weeks, despite the cold weather, to make sure the plants go dormant first. 

While extreme temperatures could injure the crowns, the risk of mulching them before dormancy could do more harm than good, and snow will help insulate the crowns anyway.

Determining if the Plants Have Gone Dormant

To determine if the plants have gone dormant and it is time to spread mulch, Poppe and other strawberry experts recommend the "plywood test." 

Once you think the plants may have reached dormancy, place a piece of plywood over a few of your strawberry plants. Wait a couple of days. If the leaves of the plants under the straw have turned yellow, then the plants were not yet dormant. If they remain green, they were dormant at the time the plywood was applied and it is ok to put down straw.

How much straw to apply

Apply 2.5 to 3.0 tons of straw per acre, covering the plants by 2 to 3 inches. 

For more information

Mulching Strawberries for Winter Protection - Rich Marini, Penn State University

Mulching Strawberries - Richard Jauron, Iowa State University