AMES, Iowa—Chrysanthemums reach their peak when most annuals and perennials are winding down for the season. Mums offer gardeners a wide range of colors and flower forms and only require moderate levels of maintenance.
Horticulturists with Iowa State University Extension and Outreach tell how to get the most enjoyment out of mums. Gardeners with additional questions should contact Hortline at email@example.com or 515-294-3801.
Chrysanthemums have shallow, fibrous roots. Repeated freezing and thawing of the soil (because of a lack of snow cover) in winter can heave mums up out of the ground, severely damaging or destroying the plants. The publication Growing Chrysanthemums in the Garden can be downloaded from the Extension Online Store at https://store.extension.iastate.edu/.
Several things can be done to increase the likelihood of garden mums surviving the winter in Iowa. Select early flowering cultivars that are known to possess excellent cold hardiness. For example, many of the University of Minnesota introductions perform well in Iowa. Plant mums in spring. Fall planted mums usually don’t survive the winter. Stop fertilizing plants in July to discourage late season growth. Finally, cover plants with a protective winter mulch in late fall.
Cover garden mums with a protective winter 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 good mulch as they tend to mat down and don’t provide adequate protection. The mulch should remain in place until early April.
Unfortunately, fall planted garden mums usually don’t survive the winter even when given winter protection. Flowering mums purchased in late summer or early fall should be regarded as temporary additions to the landscape. Spring is the best time to plant mums in Iowa. Spring planted mums have the entire growing season to get established and usually survive the winter much better than those planted in fall.
Florist mums are sold throughout the year at floral shops, supermarkets and other retailers. Unfortunately, florist mums do not perform well when planted outdoors. Most florist mums will not survive the winter when planted outdoors in Iowa. Those florist mums that manage to survive the winter typically don’t bloom outdoors. Florist mums bloom late in fall. Oftentimes freezing temperatures destroy the flower buds before they are able to fully develop and open. It’s usually best to toss a florist mum in the compost pile after blooming. If you would like to plant mums in your garden, purchase garden mums at a local garden center in spring. Garden mums are more cold hardy than florist mums. They also bloom earlier than florist mums.