Growing Chrysanthemums in Iowa

red mums — Mums are popular fall-blooming plants. ⁽¹⁾

Chrysanthemums (Chrysanthemum × morifolium) bloom in early fall when most annuals and perennials are winding down for the season. Mums are available in a wide range of flower colors and forms.

Flowering Habit

mums delayed in flowering by street light — Mums require long nights to bloom. The yellow mums in the lower left corner are not blooming on the side that faces the street light because they do not get long nights on that side of the plant. ⁽²⁾

Chrysanthemums are photoperiodic. Photoperiodic plants bloom in response to day length. Specifically, mums are short-day plants that bloom in response to short days and long nights. Plants will initiate flower buds as the day length gets shorter and the nights get longer in late summer. If anything interrupts the night length, the plants may flower later (or not at all).

Garden Mums vs. Florist Mums

Florist mums are sold throughout the year at floral shops, supermarkets, and other retailers. When planted outdoors in Iowa, florist mums do not perform well. Most florist mums will not survive the winter when planted outdoors in Iowa. Those florist mums that manage to survive the winter typically do not bloom outdoors. Florist mums require a long period of uninterrupted darkness. As a result, florist mums bloom late in fall when grown outdoors. Often, freezing temperatures destroy the flower buds before they can fully develop and open.

Garden mums are more cold-hardy than florist mums. Plants also have a shorter dark period requirement, resulting in most cultivars blooming by early fall in Iowa.

Planting

Time of Year

Spring is the best time to plant garden mums in Iowa. While many mums are available at garden centers in early fall, those planted in late summer or early fall often do not survive the winter. This is particularly true for florist mums but also applies to hardy garden mums as the plants don't have enough time to fully establish before winter.

young mum plants — Mums are best planted in spring as young plants. ⁽⁵⁾

Planting Site

When selecting the planting site, choose an area that receives at least 6 hours of direct sun per day. Avoid sites near outdoor lights as the light may inhibit flower formation.

Chrysanthemums grow 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 (compost, peat, or well-rotted manure).

How to Plant

Plant garden mums at the same depth as they are growing in their containers. Space plants 18 to 24 inches apart. After planting, water the mums with a dilute fertilizer solution. Continue to water plants regularly for 2 to 3 months.

Care of Garden Mums

mums in containers — Mums can be treated as perennials and planted in spring or treated as annuals and planted in fall. ⁽⁶⁾

Watering

Garden mums like a consistent supply of moisture throughout the growing season. Place 2 inches of mulch (woodchips, shredded bark, chopped leaves, etc.) around plants to conserve soil moisture. Water plants every 7 to 10 days during prolonged dry periods.

Fertilizing

Fertilize garden mums by applying a slow-release fertilizer around plants when new growth begins in spring. Mums respond very well to regular fertilization. Avoid over-fertilization, which can create lanky, floppy plants.

Pinching

Most garden mums benefit from pinching plants 2 or 3 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, pruning shears, or hedge clippers. New lateral shoots will develop along the stems. Pinch again when these new shoots reach a length of 6 inches. Continue pinching until early July. Do not pinch after Independence Day, as this could result in delayed flowering.

mums in the landscape — Pinching mums in spring creates plants that are bushier and less likely to flop open. ⁽⁷⁾

Care of Florist Mums

Florist mums are found throughout the year in stores and florist shops. These colorful potted plants are intended for indoor decor or annuals. In the home, place the mum in a brightly lit, cool location. An ideal site is near a window that receives bright light (but no direct sunlight) and temperatures of 60 to 70°F.

Check soil moisture frequently. When the soil surface becomes dry to the touch, water the plant until water begins to flow out the bottom of the pot. The pots of most potted mums are placed inside decorative pot covers. When watering the plant, carefully remove the pot covering, water the plant in the sink, then drop the mum back into the pot cover.

Compost plants when flowering has finished. The varieties of mum sold as flowering potted plants at the florist are not winter hardy in Iowa and cannot be successfully planted outdoors.

Propagation

vegetative mums — To propagate by cuttings, cut non-blooming stems in spring or early summer. ⁽⁸⁾

Division

Garden mums usually perform best when divided every 2 or 3 years. Divide mums in early spring as soon as new growth appears. Dig up the entire plant clump. Using a large knife, cut out the old central portion of the clump and discard it. Cut the remaining portion into sections. Each section should have several shoots and a good root system. Immediately replant the sections. Learn more here: How to Divide and Transplant Perennials.

Cuttings

Collect cutting material in spring or early summer. When the shoots are several inches tall, cut off the upper 3 to 4 inches with a sharp knife. Pinch off the leaves on the lower portion of the cuttings. Dip the bottom of the cuttings in a rooting hormone. Then, stick the cuttings in a rooting medium of coarse sand or perlite. Keep the rooting medium moist. The cuttings should root in 4 to 5 weeks.

When the cuttings have good root systems, remove them from the rooting medium and transplant the rooted cuttings into pots or plant directly into the garden.

Winter Survival

mums in baskets — Mums purchased and planted in the fall are not as likely to survive the winter. ⁽⁹⁾

Although more cold hardy than florist mums, garden mums may be severely damaged or completely destroyed in winter. Chrysanthemums have shallow, fibrous roots. Repeated freezing and thawing of the soil (because of a lack of snow cover) in winter can heave plants out of the ground, making them vulnerable to winter damage.

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. Do not fertilize plants in summer to discourage late-season growth. Do not cut down plants in the fall. Research has found that garden mums survive better if the old growth is left standing through the winter.

Apply a protective mulch over the plants in late fall. Mulch helps keep the soil uniformly cold after it has frozen, thus eliminating the alternate freezing-thawing cycle and the resulting soil heaving. Apply several inches of straw or pine needles over the plants in late November or early December. Leaves tend to mat down, possibly damaging plants. Remove the mulch in early spring (typically late March or early April).

History

The chrysanthemum is native to China and was cultivated as a crop as early as 15 centuries BC. Chrysanthemums were introduced to Japan in the eighth century AD and later became a symbol used on the Imperial Seal of Japan. The chrysanthemum was introduced to Europe in the 1600s and to the United States during the colonial period.

Types of Chrysanthemums

different mum types — Mums have many different flower shapes and styles. ⁽¹⁰⁾

Chrysanthemum classification is based on the shape and arrangement of the petals. The following are the major types and their characteristics.

Anemone: Long, large petals surround a center covered by short, deeper-colored petals; most cultivars are hardy.

Cushion: Often called “azalea” mums; low bushy plants flower early; most cultivars are hardy.

Decorative: Several rows of petals are “incurved” (close, regular petals curving toward the flower center), “incurving” (loose, irregular petals curving toward the flower center), or “reflexed” (all petals curving away from the flower center), many hardy cultivars available.

Pompon: Small, stiff, almost globular flowers; some hardy cultivars.

Quill: Long, straight, tubular petals; few hardy cultivars.

Single: Daisy-like flowers with several rows of long petals radiating from a flat center; many hardy cultivars.

Spider: Long, tubular petals with curled ends; few hardy cultivars.

Spoon: Spoon-shaped petals; some hardy cultivars.

More Information

Photo credits: 1: Cindy Haynes; 2: Aaron Steil; 3: Cindy Haynes; 4: Hanna Tor/AdobeStock; 5: Lora/AdobeStock; 6: Aaron Steil; 7: Cindy Haynes; 8: supersomik/AdobeStock; 9: Aaron Steil; 10: Aaron Steil

Authors:

Aaron Steil

Last reviewed:

September 2024