Potted chrysanthemums, commonly known as mums, signal the arrival of autumn with their vibrant displays. These plants are often purchased in full bloom, serving as temporary seasonal decorations. Although many people treat them as annuals and discard them after the flowers fade, the chrysanthemum is a perennial that can be transitioned into a permanent garden feature. This transition requires specific care steps after the initial color passes, preparing the plant for winter and setting the stage for future autumn reblooms.
Immediate Post-Bloom Maintenance
The first action after the blooms have completely faded is deadheading. Removing the spent flower heads prevents the plant from diverting energy into seed production. This technique encourages the plant to focus resources back toward its root system, which is important for surviving the dormant winter period.
Following deadheading, cut the plant stems back significantly, reducing the height to approximately two to six inches above the soil line. This pruning eliminates diseased or damaged foliage, improving air circulation and reducing fungal pathogens during cooler, wetter months. During this post-bloom phase, maintain consistent, light moisture in the potting medium.
Keep the soil slightly damp but never saturated, as overly wet conditions can lead to root rot as the plant slows its growth. Maintaining controlled moisture is important for potted plants, which are more susceptible to both drying out and becoming waterlogged than plants in the ground.
Identifying Hardy Versus Florist Varieties
The next step for your mum depends entirely on whether it is a hardy garden variety or a florist variety. Hardy mums are perennial types, typically labeled with their USDA hardiness zones, usually surviving winters in Zones 4 through 9. Florist mums are genetically bred for dense, spectacular fall displays, often with little visible foliage, and are not selected for winter hardiness.
A key distinction is the root mass; florist mums are frequently root-bound and lack the runners (stolons) that hardy varieties produce to help them spread. If the pot has no tag, assume the plant is a less-hardy florist type, especially if the blooms are dense and the plant was purchased from a grocery or big-box store. This identification governs the overwintering strategy.
Strategy for Overwintering the Plant
The overwintering method must align with the plant’s hardiness level to ensure survival through the cold season. For confirmed hardy garden mums, transplant them directly into the ground before the first hard freeze occurs. Select a location with well-draining soil, as waterlogged roots are susceptible to freezing and subsequent damage.
After planting the mum, apply a thick layer of dry, airy mulch, such as straw or pine needles, around the crown of the plant. This layer should be three to four inches deep and is applied once the ground begins to freeze. The purpose of this insulation is to maintain a consistently cold temperature and prevent cycles of freezing and thawing that can push the plant’s roots out of the soil.
If the plant is a florist mum, or if the winter climate is too severe for outdoor survival, overwinter the plant in a state of indoor dormancy. Move the potted plant to a protected location, such as an unheated garage, basement, or shed. The ideal temperature range for this dormant period is cool, remaining just above freezing (32 to 50 degrees Fahrenheit).
During dormancy, the plant requires very little light and minimal moisture. Check the soil every few weeks, adding only enough water to prevent the roots from completely drying out. Overwatering is the most common cause of failure in this protected storage method, often leading to root rot.
Preparing the Mum for Rebloom in Spring
As the last threat of severe frost passes in early spring, dormant mums need to be awakened and prepared for the growing season. Plants stored indoors should be gradually introduced to increasing light levels and warmer temperatures over one to two weeks. Once new green growth emerges, trim all the previous year’s dead stems and foliage away to the ground.
If a plant is still in its original pot and appears root-bound, repot it into a slightly larger container with fresh soil to encourage root expansion. The key step for achieving a dense, dome-shaped plant with abundant fall blooms is a technique called “pinching.” When new growth is about six inches tall, remove the top inch or two of each stem to encourage side branching. Repeat this pinching every few weeks until the summer solstice or no later than early July, allowing the plant time to set its fall flower buds.