Chrysanthemums, commonly known as mums, are a staple of autumn gardens, offering a vibrant burst of color when most other flowers have faded. While they can be planted outside, achieving long-term survival depends entirely on the variety selected and the specific planting techniques used. Mums are technically perennials, meaning they can return year after year, but their success as a permanent garden fixture is determined by their genetic hardiness and the care they receive. Understanding the different types of mums and their environmental needs is the first step toward successfully incorporating them into an outdoor landscape.
Understanding Garden Mums Versus Florist Mums
The longevity of a chrysanthemum planted outside hinges on the difference between two commercially available types. “Hardy Garden Mums,” often labeled as perennial or cushion mums, are bred to withstand colder temperatures, typically surviving winters in USDA Hardiness Zones 5 through 9. These varieties have a more open, naturally branching growth habit and robust root systems that establish deeply in the soil over a full growing season.
The second type, “Florist Mums” or “Pot Mums,” is frequently sold in the fall for seasonal decoration. These plants are usually forced into a dense, ball-like shape with flowers that hide the foliage. Florist mums lack the genetic cold tolerance and established root mass needed to reliably survive winter outdoors. Due to their intensive greenhouse production and shallow root systems, they are best treated as decorative annuals, especially in colder climates.
Selecting the Optimal Location and Preparing the Soil
Successful outdoor planting requires careful consideration of the environment to encourage deep root establishment. Chrysanthemums thrive best in full sunlight, requiring a minimum of six hours of direct sun exposure daily. Adequate light is necessary to produce strong stems and abundant, high-quality blooms in the fall. Avoid planting them near artificial light sources, such as streetlights, as this can interfere with the plant’s natural photoperiodic response that triggers bud formation.
The condition of the soil is equally important because mums are highly susceptible to root rot if they remain in perpetually wet conditions. Excellent drainage is mandatory for any planting location. To ensure this, amend the garden bed with a generous amount of organic matter, such as compost or well-rotted manure, before planting. Organic material improves the soil’s structure, allowing excess water to drain away while retaining necessary moisture and nutrients.
Best Timing and Technique for Outdoor Planting
The timing of planting is the most significant factor in determining if a mum will successfully become a perennial. Planting hardy mums in the early spring, after the last expected frost, is preferred for long-term survival. Spring planting provides the entire growing season for the plant to develop a deep, extensive root system before the ground freezes. This robust root structure allows the plant to survive the stresses of winter dormancy.
If planting later in the season, such as in the fall, do so at least six weeks before the first hard frost to allow for root establishment. Fall-planted mums often fail to return because their root systems lack sufficient time to anchor and store energy for winter. When planting, the hole should be dug at least twice as wide as the root ball but no deeper. Set the plant into the ground at the same level it was in its container. Adequate spacing of 18 to 24 inches between plants promotes air circulation and helps prevent foliage diseases.
Essential Care for Long-Term Outdoor Survival
Consistent moisture management is necessary throughout the growing season, particularly during dry spells. While mums require regular watering, the soil must never become waterlogged, which quickly leads to root problems. Deep, infrequent watering is preferable to shallow, frequent applications, as this encourages the roots to grow downward rather than remaining near the surface.
To cultivate a dense, bushy plant with abundant flowers, a process called “pinching” must be performed during the spring and early summer. Starting when the new spring shoots are about six inches tall, remove the top two to three inches of the stem. This removal of the terminal bud forces the plant to branch out laterally, resulting in a greater number of flower buds. Repeat this pinching process every few weeks until mid-July, as later pruning can remove the developing flower buds.
Proper winterization is the final step to ensure long-term survival, especially in colder climates. After the plant has finished blooming and the foliage has died back from hard frosts, cut the stems down to about three to four inches above the ground. Apply a thick layer of loose, airy mulch, such as straw or pine needles, over the planting area once the ground has frozen. The purpose of this mulch is to maintain a consistent soil temperature, preventing the repeated freeze-thaw cycles that can heave the root crown out of the soil.