Yard and Garden: Preparing Gardens for Winter



AMES, Iowa – As the temperatures start to drop, some gardeners wonder how to prepare their garden and plants for the winter months. All plants need attention going into winter and there are many methods to provide winter protection. Horticulturists with Iowa State University Extension and Outreach give tips and suggestions on how to prepare the garden for an Iowa winter.

To have additional questions answered, contact ISU Hortline at 515-294-3108 or hortline@iastate.edu.

How should I prepare hybrid tea roses for winter? 

Modern, bush-type roses, like hybrid teas, floribundas and grandifloras, require protection during the winter months. The low temperatures and rapid temperature changes in winter can severely injure and sometimes kill unprotected roses. Hilling or mounding soil over the base of each plant is an excellent way to protect bush-type roses.

Begin by removing fallen leaves and other debris from around each plant. Removal of diseased plant debris helps reduce disease problems next season. Next, cover the bottom 10 to 12 inches of the rose canes with soil. Place additional material, such as straw or leaves, over the mound of soil. A small amount of soil placed over the straw or leaves should hold these materials in place. Prepare modern roses for winter after plants have been hardened by exposure to daytime temperatures in the forties and nighttime temperatures in the twenties. Normally, this is early November in northern Iowa, mid-November in central areas, and late November in southern counties. 

How should I prepare my strawberry bed for winter? 

Strawberries should be mulched in fall to prevent winter injury. Cold winter temperatures and repeated freezing and thawing of the soil through the winter months are the main threats to strawberry plants. Temperatures below 20 degrees Fahrenheit may kill flower buds and damage the roots and crowns of unmulched plants. Plants can be destroyed by repeated freezing and thawing of the soil which can heave unmulched plants out of the ground. 

Allow the strawberry plants to harden or acclimate to cool fall temperatures before mulching the bed. 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. The depth of the mulch should be three to five inches at application.  The material should eventually settle to two to four inches. 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.

Leaves are not a good winter mulch for strawberries. Leaves can mat together in layers, trapping moisture. A leaf mulch may actually damage plants due to excess moisture trapped under the material. 

How should I prepare garden mums for winter? 

Chrysanthemums are shallow-rooted plants. Repeated freezing and thawing of the soil during the winter months can heave plants out of the ground and cause severe damage or even death.

Gardeners can increase the odds of their mums surviving the winter by applying mulch in fall. Mulching helps eliminate the alternate freezing-thawing cycles that can heave plants out of the soil. Apply the mulch in late fall, typically late November in central Iowa. Do not cut back the plants prior to mulching. Simply cover the plants with several inches of mulch. Suitable mulching materials include clean straw, pine needles, and evergreen branches. Leaves are not a good mulch as they tend to mat down and don’t provide adequate protection. The mulch should remain in place until early April.