Chrysanthemums, also called mums, are hardy, long-lived perennials that generally bloom from October to December when grown in the garden. Chrysanthemums are triggered to bloom only when the nights are long enough. During summer, when days are long and nights are short, chrysanthemums in the garden grow vegetatively. As the period of nighttime darkness increases in late summer and early fall, flower bud initiation occurs. This generally takes place here in August and September with flowers opening in October through December. Plants generally stay in full bloom for about three weeks.
Blooming plants are available at nurseries, however, as early as August. The chrysanthemums you see blooming earlier in nurseries have either been grown up north (where days get shorter earlier in the season) or were stimulated to bloom by artificially lengthening the number of hours of darkness they receive each day.
It is important to choose the right type of chrysanthemum for your landscape. Chrysanthemum varieties are grouped into cut-flower mums, pot mums and garden mums.
Cut-flower mums are selected for their ability, when cultivated properly, to produce spectacularly large flowers with long, strong stems suitable for cutting. The so called “football mums” popular for corsages are in this category. Some cut-flower varieties produce clusters of smaller flowers on long stems and are commonly available at florist shops year-round.
Pot mums were developed to produce a beautiful container plant with large flowers. They are grown in greenhouses and must be pinched, disbudded and even treated with growth regulators to produce a shorter, more attractive finished product. Growers can produce blooming pot mums all year. Artificially lengthening the night during summer by covering the plants in late afternoon with black cloth induces them to bloom out of season. These are the mums commonly available in pots at florist shops.
Neither cut-flower mums nor pot mums are generally suitable for the flower garden. Both tend to grow tall and leggy in the garden, resulting in plants that are floppy and unattractive, even though the flowers may be pretty.
The best chrysanthemums for planting in the landscape are garden mums. These mums are bred and selected for growing in the garden. They are short, bushy plants about 12 to 18 inches tall that literally cover themselves with clusters of small 1½-inch flowers in virtually every color except blue. This type of mum is available now at nurseries and garden centers in 4-inch, 6-inch and gallon-size containers.
Select plants with mostly closed buds and healthy foliage when purchasing garden mums. Plants already in full bloom will not be attractive as long. Avoid plants whose flowers have already begun to fade or those that have broken branches and yellow foliage.
Some gardeners use mums as temporary color in the landscape. When the flowers fade, they remove the plants and replace them with cool-season bedding plants. However, chrysanthemums will bloom in the fall garden for many years if grown properly.
Chrysanthemums should be planted in well-drained beds that receive at least six hours of sun. After they finish flowering, garden mums should be cut back about one-quarter their height. In late January or early February, cut them back to about 3 inches from the ground. New growth usually begins in February or March when new shoots appear at the base of the old stem stubs.
When you see the new shoots, it is a good idea to dig up the whole clump and divide it into two to four sections. Replant them where you want them to grow, spacing the divisions about 12 inches apart. Discard the brown, woody middle of the plant and just plant the vigorous shoots from around the outside. Dividing the mums annually makes them strong and vigorous and allows you to keep control over them.
Mums require no special care during the year. Fertilize them with a general-purpose fertilizer when you fertilize your other flowers. Water them thoroughly during periods of drought, and keep them well mulched to reduce competition from weeds. Pinch the tips of vigorously growing shoots occasionally during the summer to encourage bushiness. Do not pinch or prune mums after mid-July.
Plant some beautiful mums and welcome the fall season with brilliant color. And with proper care, they can brighten your fall garden for years to come.