Make room in your garden for the beauty of hardy mums. These easy-growing beauties have almost as many names as they do flowers. Known also as fall mums, garden mums and Belgian mums, these autumn stand-outs fall go by the botanical name Chrysanthemum x morifolium. Learn some tips on growing hardy mums, including ways to help them perform their best in your landscape.
Hardy mums fill autumn scenery with the classic colors of the season. These perennial bloomers are known for their flower power, forming mounds of color that are literally packed with petals. Hardy mums not only bring terrific color to the fall garden, but they also have a virtually pest-free personality. Few pests bother hardy mums as they strut their stuff in fall—or during the rest of the growing season, for that matter.
Despite the name hardy mums, these plants are frequently killed during winter, leaving gardeners puzzled. Are they hardy—or aren’t they? These plants have the genetics to survive winters reliably to Zone 4. So why don’t they make it through winter’s chill in northern gardens? The answer hinges on two issues: planting time and shallow roots.
When to Plant Mums
Many gardeners plant their hardy mums too late in the fall for them to overwinter successfully. These perennials have shallow root systems, and as the top few inches of soil freeze and thaw through winter, that expansion and contraction can actually push newly planted hardy mums out of soil. This displacement is called frost heave or heaving. If hardy mums experience frost heave, roots can freeze (and die), along with the plant crown or main growing point.
The best time to plant hardy mums is in spring. At this point, you’ll find smaller plants for sale than you might in fall. They likely won’t be budded or flowering, and the color selection may be minimal. But if you tuck hardy mums into soil in spring, you’ll be rewarded with a strong color show in years to come—including the one you plant.
If you want to wait for the wider color selection available in fall, purchase hardy mums as soon as you see them for sale. Plant them at your earliest opportunity. The goal is to get these plants into the ground in early fall, so they have ample time to develop strong roots. Be sure to mulch hardy mums well after a hard, killing frost. Add more mulch once the ground freezes.
As you’re considering adding hardy mums to your yard, don’t overlook Belgian mums. These hardy mums hail from Belgium and are said to offer high flower numbers (up to 1,000 per plant) and less brittle branches, which means fewer broken stems in the garden.
Another group of hardy mums, developed in Minnesota, are sold as “Mammoth Mums.” True to their name, they form large mounds in the garden—up to 5 feet across by the third year. These garden mums are bred to survive Minnesota winters.