Chrysanthemums (mums) symbolize autumn, providing a final burst of color as summer plantings fade. Often purchased in full bloom, gardeners frequently question the proper care once the initial display diminishes. Whether to continue pruning spent blooms, a practice known as deadheading, becomes confusing as the weather cools and the plant prepares for dormancy. Understanding the mum’s biological response to this late-season maintenance is key to ensuring its health and potential survival for the following year.
Defining Deadheading and Its Purpose
Deadheading is the horticultural technique of removing faded or spent flower heads from a plant. This light pruning manipulates the plant’s natural reproductive cycle. A plant’s biological imperative is to produce seeds after flowering, diverting energy toward seed development once flowers fade.
Removing spent blossoms before seeds set tricks the plant into redirecting that energy into vegetative growth or producing additional flower buds. Performing this task during the summer results in a bushier plant and a longer, more profuse display of flowers.
The Specifics of Fall Deadheading
While deadheading is beneficial during summer, the practice requires caution in late fall. Cutting stimulates the plant to produce new growth hormones, resulting in tender shoots and leaves highly susceptible to cold temperatures. This new growth will not have sufficient time to “harden off” before the first significant frost arrives.
If frost kills this new growth, the damage can travel down the stem, weakening the plant and making it vulnerable to winter kill. Extensive deadheading or cutting back stems should cease by late summer, typically around early September.
After this cutoff, only lightly pluck or pinch off the most unsightly, fully spent flower heads for aesthetic purposes. Avoid cutting into any green, leafy stems that might encourage a flush of vulnerable new growth before winter dormancy.
Essential Fall Care Beyond Deadheading
Preparing chrysanthemums for winter requires protecting the plant’s crown and root system rather than stimulating new top growth. A common mistake is cutting the entire plant back to the ground immediately after blooming. Instead, leave the dead foliage and stems standing throughout the winter, as they provide natural insulation and trap snow, protecting the roots.
Once the ground is consistently cold or frozen, apply a thick layer of winter mulch around the plant’s base. This protective layer, ideally 3 to 4 inches deep, should consist of a non-packing material such as straw or shredded leaves.
The mulch maintains a consistent soil temperature, preventing damaging freeze-thaw cycles that can heave the plant out of the ground and damage the root system. Proper watering leading up to dormancy is also important; ensure the plant is well-hydrated until the ground freezes, then stop supplemental watering until spring.