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Chrysanthemums Add Color to Fall Gardens

Updated September 03, 2021

Kristine Lang

Assistant Professor & SDSU Extension Consumer Horticulture Specialist

Additional Authors: David Graper
Four varieties of colorful chrysanthemum flowers, including: Mammoth Red, Mammoth Lavender, Mammoth Yellow Quill and Mammoth Twilight Pink.
Figure 1. Chrysanthemums come in a variety of colors to brighten your garden in the fall. A reliable series of hardy perennial mums is the Mammoth series developed by the University of Minnesota. Courtesy: David Graper and Kristine Lang.

Original article by David Graper, former SDSU Extension Horticulture Specialist and Master Gardener Program Coordinator. Updated by Kristine Lang, Assistant Professor and SDSU Extension Consumer Horticulture Specialist.

Chrysanthemums are the quintessential fall-blooming plant that are sold all over the region. They are prized for their beautiful display of flowers that add so much color to our landscapes and patios each autumn. They are a favorite of gardeners everywhere and have commonly become known simply as mums, which certainly has a nice homey sounding name. But not all mums are created equal! You need to shop carefully if you want plants that will look good this fall, come back in future years and bloom before a hard freeze puts an end to their floral display in the fall.

Photoperiodic Plants

Two colorful chrysanthemum varieties: Mammoth Red Daisy and Mammoth Lavender Daisy.
Figure 2. A) Mammoth Red Daisy. B) Mammoth Lavender Daisy. Courtesy: David Graper.

Chrysanthemums, like many fall-blooming plants, are photoperiodic. This means that they develop flower buds in response to the length of the night. As daylight hours get shorter and shorter in late summer, the length of the night period increases. Once the nights get long enough, the flower initiation process begins.

The earliest varieties of the hardy garden mums that we can grow in South Dakota need seven to nine weeks of long nights to come into flower. Later-flowering varieties might need 10 to 16 weeks of long nights, which means that most of these will probably not flower before we have a heavy frost, which will damage the flower buds and prevent them from flowering. The early flowering types, like the ‘Mammoth Pink’ developed at the University of Minnesota, may start flowering as early as mid-August, which will allow us to enjoy their flowers for four weeks or more.

Selecting Chrysanthemums for the Garden

Two colorful chrysanthemum varieties: Mammoth Yellow Quill and Mammoth Twilight Pink.
Figure 3. A) Mammoth Yellow Quill. B) Mammoth Twilight Pink. Courtesy: Kristine Lang.

There are many different varieties of garden mums with varied flower forms ranging from the double-flowered cushion mums to the single-daisy types, the larger decorative pompons, down to the button mums with their small, double flowers.

Most mums will likely be blooming if you buy them in the fall of the year. But remember, not all mums you buy this fall can be planted and overwinter successfully in South Dakota gardens. So, while the bright displays of chrysanthemums might look great when you buy them this year, you may never get to see them flower again in your garden if they are not well-adapted to our climate. Seek out your local garden center or greenhouse to source hardy perennial mums that will bloom well in South Dakota.

Chrysanthemum Care

Mums should be grown in full sun and in a well-drained soil. Keep in mind that some varieties of chrysanthemums can grow quite large. The Mammoth mums from Minnesota are aptly named, because a single plant can grow to three feet in diameter and be covered in blooms.

Chrysanthemums can be planted right after you purchase them to enjoy in the fall; although, the plant is using a lot of energy to produce blooms, so plant it as soon as possible to give your mum the best chance of rooting in ahead of winter. Hardy perennial chrysanthemums can also be purchased and planted in the spring months. Spring is also a good time to divide large plants and share them with your friends. Some people will shear the tops of their mums in mid-summer to encourage more branching and more flowers later – this is called pinching. Do not prune mums after August first or you can interfere with the floral initiation process and end up with fewer flowers than if you had not sheared them at all.

After the flowers and plants freeze in the fall, you can cut back the foliage to the base of the plant or leave the foliage to catch snow and protect the plant. If you cut the foliage back, you may want to add some additional mulch after the ground has frozen to protect the small buds that have already formed at the base of the plant. Those buds will grow out to produce the stems for next year.

Special thanks to SDSU Extension Master Gardeners Tim Schreiner and Stacy Dreis for serving as volunteer copyeditors of this article.

Related Topics

Flower, Master Gardener