AMES, Iowa – It’s time to think about protecting strawberry plants from the winter elements. Horticulturists with Iowa State University Extension and Outreach explain how to properly mulch strawberries to provide protection against winter injury. To have additional yard and garden questions answered, contact the ISU Hortline at 515-294-3108 or email firstname.lastname@example.org.
Strawberries should be mulched in fall to prevent winter injury. Low temperatures and repeated freezing and thawing of the soil through the winter months are the main threats to strawberry plants. Temperatures below 20 F may kill flower buds and damage the roots and crowns of unmulched plants. Repeated freezing and thawing of the soil can heave plants out of the ground, severely damaging or destroying the plants.
Allow the strawberry plants to harden or acclimate to cool fall temperatures before mulching the bed. Applying a mulch before the strawberry plants have hardened-off properly may make plants more susceptible to winter injury. In northern Iowa, strawberry plantings are normally mulched in early November. Gardeners in central and southern Iowa should mulch their strawberries in mid-November and late November, respectively.
Excellent mulching materials include clean, weed-free oat, wheat or soybean straw. Chopped cornstalks are another possibility Apply approximately 3 to 5 inches of material. After settling, the mulch layer should be 2 to 4 inches thick.
Leaves are not a good winter mulch for strawberries. Leaves can mat together in layers, trapping air and creating space for ice to form. The leaf, air and ice layers do not provide adequate protection. A leaf mulch may damage plants due to excess moisture trapped under the material.
In windy, exposed areas, straw mulches can be kept in place by placing wire or plastic fencing over the area. The fencing can be held in place with bricks or other heavy objects.