Chrysanthemums: The shining star of fall landscapes

Autumn is approaching quickly, and one of the landscape plants we most commonly associate with the fall is the chrysanthemum, frequently referred to simply as 'mum.' Fall flowers are often in short supply, compared to the relative abundance of blooms in spring and summer, and yet reliably year after year, chrysanthemums are the shining star of fall landscapes with their late-arriving blossoms.
 
Chrysanthemums are short-day blooming plants, meaning their bloom is triggered by the shortening length of daylight and increase in length of darkness that occurs each fall. They are members of the Asteraceae, or daisy, family, with flowers resembling the classic disk-shape we associate with daisies. Many of the mums we buy and plant in the fall are herbaceous perennials, though gardeners treat them like annuals, ripping them out after the flowers have succumbed to frost.

Photo, above: Chrysanthemums stems & leaves. Photo credit: Daba, CC BY-NC 4.0
Photo, above right: 'Cathy's Rust' flowers, in November. Photo credit: Cathy DeWitt, CC BY-NC-ND 4.0

Photo, immediately above: 'Mary Stoker' Chrysanthemums.

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Though there are several different types of chrysanthemums, and thousands of cultivars, all of the mums we use in North Carolina like essentially the same conditions, preferring well-drained, high organic matter soils in full sun. They will do okay in a small amount of shade, too, and an hour or two of late afternoon shade may even be a good idea, but more than that will reduce the amount of blooms you see. Mums do use a fair amount of water, particularly large, container-grown mums, but they don’t like to be in wet soil, so adequate drainage is quite important.
 
If you’re planting mums this fall and want to overwinter them, you will need to do a bit of work in the spring and summer to duplicate the show you get in year one. Container-grown mums are pinched back repeatedly throughout the growing season in order to develop large dome-shaped plant shapes and they will need to be pinched back that same way in subsequent years in order to grow to the same size and shape the following year. Even the so-called hardy mums, which are treated more like traditional perennials, including cultivars such as ‘Sheffield Pink’ and ‘Mary Stoker,’ should be pinched back for peak performance.    

Above: 'Sheffield Pink' Chrysanthe-mums are an example of hardy mums, which are treated like traditional perennials.

Above: Pinch back mums in a container to retain their large dome-shaped and size the following year.

Use mums in your landscapes in containers or in the ground, in lining walkways, edging along the front of a border area, or along a wall or other high-visibility areas. Mums can also be used as companion plants with asters, ornamental kale and cabbage, and other plants that stand out in the fall. Mums can develop some leaf spot fungal diseases, but avoiding watering the foliage and instead directing water to the root area of the plants will lessen those issues. 
 
While mums have relatively low toxicity, there is an oil in the leaves and flowers that can cause redness and irritation in some individuals sensitive to the compound. There is also a natural insecticide made from an extract from chrysanthemum flowers and seeds.
 
Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center.  If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705.