Deadheading is the act of removing spent flowers from the popular fall-blooming chrysanthemum, or mum, encouraging new blooms. Mums are perennials, but their survival depends heavily on the timing of fall maintenance. Deadheading redirects the plant’s energy away from seed production and toward additional flowers or root establishment. Knowing when to stop this activity is necessary for ensuring the plant’s long-term health.
Fall Deadheading: Weighing New Blooms Against Winter Survival
The answer to whether you should deadhead mums in the fall is generally yes, but only up to a certain point. Removing faded blooms throughout early fall extends the plant’s flowering period until the first hard frost. This practice helps the plant conserve energy by interrupting the natural process of setting seed.
However, the timing threshold is critical for perennial mums planted in the ground. Late-season deadheading can stimulate tender, new vegetative growth poorly prepared for freezing temperatures. This soft new growth lacks the hardened cell structure needed to withstand frost, and its subsequent death can compromise the plant’s crown and root system. Gardeners should cease all deadheading by early to mid-fall, allowing the plant time to slow its growth and allocate resources to its shallow root system for winter protection.
The Difference Between Deadheading and Hard Pruning
Gardeners often confuse deadheading with hard pruning, yet these are two distinct maintenance tasks. Deadheading focuses solely on removing the dead flower heads, which encourages the plant to produce more blooms or dedicate energy to its roots. This action is done while the plant is actively flowering and is primarily a cosmetic or bloom-extending measure.
Hard pruning, or cutting back, involves significantly reducing the overall height of the plant’s stems. This task is a measure for winter preparation, not for encouraging new flowering. Cutting back is typically done after the foliage has died back or after the first hard frost. The remaining stem structure, often left at four to six inches, helps anchor the plant and allows for better air circulation around the crown.
Essential Steps for Winterizing Mums
Successful winterization requires protective steps because chrysanthemums have a shallow root system highly susceptible to the freeze-thaw cycles of winter. The goal is to insulate the soil and maintain a consistently cold temperature to prevent “frost heaving.” Frost heaving occurs when repeated freezing and thawing pushes the plant’s crown out of the soil, exposing the roots to damaging cold and desiccation.
Applying a protective mulch layer is the most important step for overwintering mums in the ground. Mulch should be applied in late fall, usually after the ground has frozen or after the first hard frost. Suitable materials include loose, airy options such as clean straw, pine needles, or evergreen boughs, which provide insulation without compacting or retaining excessive moisture. Avoid heavy materials like leaves, which can mat down and suffocate the plant’s crown.
A layer of mulch approximately four to six inches deep should be placed around the base of the plant, extending out to the drip line. This depth helps prevent the soil temperature from fluctuating widely throughout the winter months. Before applying this heavy mulch, ensure that the plant’s roots are well-hydrated, as adequate moisture helps the root tissues endure freezing temperatures. The protective mulch should remain in place until the threat of severely cold weather has passed in the spring, typically by early to mid-April.