AMES, Iowa – With colder temperatures sweeping across Iowa, it’s time to start thinking about winter. How should Iowans prepare flowers for winter temperatures to ensure their long-term survival?
Iowa State University Extension and Outreach horticulturists can help answer questions about the best way to prepare flowers for winter. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.
How should I prepare roses for winter?Modern roses, like hybrid teas, floribundas and grandifloras, require protection during the winter months. Low temperatures and rapid temperature changes in winter can severely damage and sometimes destroy unprotected roses. (Most old garden roses possess excellent cold hardiness and don’t require winter protection.)
Hilling or mounding soil over the base of each plant is an excellent way to protect modern roses. Begin by removing fallen leaves and other debris from around each plant. Removing 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 40s and nighttime temperatures in the 20s. Normally, this is early November in northern Iowa, mid-November in central areas and late November in southern counties.
How should I prepare 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 improve the odds of their mums surviving the winter by mulching plants in fall. Mulching helps eliminate the 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 (weed-free) 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.
How do I prepare tree peonies for winter?Tree peonies are small, woody shrubs. Unlike herbaceous peonies, the stems of tree peonies do not die back to the ground in fall.
