Think fall and think flowers, and you’re probably thinking chrysanthemums—or “mums,” as they are commonly known. Colorful potted mums pop up this time of year at grocery stores, florist shops, home centers and nurseries, ready for harvest-themed tabletop arrangements and fall decor.
What many people don’t know, however, is that pot mums grown as annual flowers are not the true garden mums intended for planting in the landscape.
Typical florist pot mum varieties are bred for growing in greenhouses and are generally not intended for perennial, outdoor plantings. When planted in a flower border, pot mums often meet a slow death after the first season. If they survive, they never flower as well as when they were purchased. Enjoy their excellent floral displays, which often last through autumn, but save yourself some frustration and simply deposit pot mums in the compost bin when the show is over.
If you want to add mums to your outdoor landscape, look for garden mums at your local garden center instead. Garden mums come in an array of bloom colors and shapes and make handsome, fall-flowering additions to a perennial border, offering years of enjoyment with little care.
When you buy garden mums to decorate indoors, resist the urge to plant them right after flowering. Your container-grown mum may not finish flowering before mid-November, and it might not be ready to face the outdoor cold at that point. Instead, remove the spent blooms, and place the container in a protected site outdoors or in an unheated room. Allow the plant to rest over the winter, then plant outside in the spring.
Select a site with well-drained soil and full sun. Mums will grow in part shade but will tend to be leggy. Before planting, prepare the soil by tilling in a fertilizer based on the results of a soil test. If no soil test was taken, add four pounds of 10-10-10 fertilizer per 100 square feet and till into the top six inches of soil. Add a two- to three-inch layer of compost at the same time.
Mums enjoy regular fertilization, but too much will promote excess growth and inhibit flowering. A dose of liquid fertilizer every two weeks during the summer will generally suffice. Stop fertilizing after the first of August.
Garden mums need to be cut back two to three times during the growing season to reduce height and encourage branching. This practice will lead to more flowers and a sturdier plant. When the stems first reach six inches tall (early June in my area of the state), remove one to two inches of growth from the top. Repeat again in early to mid-July and one final time in early August, if necessary. Flower buds will begin to develop after this and should not be removed. Spider mites and aphids are the most troublesome pests, but they can be managed with insecticidal soap or a strong stream of water.
Your plant will spread quite nicely in its new home and should be divided every three years in the spring or fall. Conveniently, this is an excellent time to share prized mums with friends. You’ll all enjoy this exuberant addition to the fall garden.
S. CORY TANNER is an area horticulture agent and Master Gardener coordinator for Clemson Extension based in Greenville County. Contact him at firstname.lastname@example.org.