AMES, Iowa – Chrysanthemums are photoperiodic, meaning they bloom in response to day length. As short-day plants, mums bloom in response to short days and long nights. There is a differece between garden mums and florist mums, those sold by retailers throughout the year. Garden mums are more cold hardy and have a shorter dark period requirement, resulting in most cultivars blooming in early fall in Iowa. Horticulturists with Iowa State University Extension and Outreach offer tips on growing and caring for garden mums. To have additional questions answered, contact Hortline at firstname.lastname@example.org or 515-294-3108.
Spring is the best time to plant garden mums (Chrysanthemum x morifolium) in Iowa. Mums planted in spring survive the winter much better than those planted in fall. Spring planted mums have the opportunity to grow and establish themselves over a period of several months. Fall planted mums have little time to establish themselves before winter and are much more likely to be severely damaged or destroyed in winter.
Chrysanthemums perform best in moist, well-drained soils. Avoid wet, poorly drained sites. Improve hard, difficult-to-work soils by incorporating 2 to 3 inches of organic matter, such as compost, peat or barnyard manure, into the soil.
Garden mums also need full sun. The planting site should receive at least six hours of direct sun per day. Avoid shady locations near trees and large shrubs.
Plant garden mums at the same depth as they are growing in their containers. Space plants 18 to 30 inches apart, depending on the mature size of the cultivar. Thoroughly water plants after planting. Continue to water on a regular basis for two to three months.
Early spring is the best time to divide chrysanthemums. Dig up plants in early spring just as new growth begins to appear. Divide each plant into sections with a sharp knife. Each division should contain several shoots and a portion of the root system. Replant the divisions immediately. Keep the newly divided plants well watered through spring and summer.
Most garden mums benefit from pinching plants two or three times in spring and early summer. Pinching produces bushier plants and additional flowers. When the new shoots are 6 inches tall, pinch out the shoot tips with your fingers, a pruning shears or hedge clippers. New lateral (side) shoots will develop along the stems. Pinch again when these new shoots reach a length of 6 inches. Continue pinching until early July. Plants pinched after early July may not have sufficient time to form flower buds and bloom before the first frost in fall.