Chrysanthemums (mums) are popular flowers that bring vibrant color to the garden, typically in the autumn. They can flower more than once, but this often requires human intervention. While the natural cycle dictates one major bloom period, specific care techniques can encourage the plant to produce multiple flushes of color within a single growing season. Understanding the plant’s flowering trigger is the first step in extending its display.
Understanding the Chrysanthemum Bloom Cycle
The timing of a chrysanthemum’s primary flowering is controlled by photoperiodism. Mums are classified as short-day plants, meaning they require a period of consistently long, uninterrupted darkness to trigger flower bud development. This darkness must typically be 12 hours or longer each night for several weeks.
This light requirement naturally aligns with the diminishing daylight hours as summer transitions into fall. When nights grow longer, the plant’s internal clock signals the shift from vegetative to reproductive growth, resulting in the dense, late-season bloom. Commercial growers often manipulate this cycle artificially with black cloth to force early or off-season flowering.
Techniques for Reblooming Through Deadheading
The primary method for encouraging a second, or even third, wave of flowers is deadheading, which involves manually removing the spent or faded flower heads. This action interrupts the plant’s natural goal of producing seeds for reproduction. By removing old blooms before they can set seed, the chrysanthemum diverts its energy. Instead of directing resources toward seed development, the plant produces new growth and subsequent flower buds, extending the overall blooming time until a hard frost occurs.
To deadhead correctly, snip the stem just above the first set of healthy leaves or a new side shoot. Use sharp, sanitized snips or scissors to ensure a clean cut that heals quickly, minimizing infection risk. Regular deadheading, perhaps once or twice a week during peak season, is necessary to keep the plant actively producing new growth.
Seasonal Care and Plant Longevity
A chrysanthemum’s long-term survival depends on whether it is a hardy perennial “garden mum” or a less cold-tolerant “florist mum,” which is often treated as an annual. Garden mums, generally hardy in USDA zones 5 through 9, possess a robust root system that can survive winter when properly established. Florist mums, often sold in full bloom in the fall, may not have developed the necessary root strength to overwinter outdoors.
For hardy mums intended to return, plant them several weeks before the first hard frost. After the final bloom finishes and the foliage browns, cut the stems back to about two inches above the soil line or leave the old foliage for winter protection. Applying a layer of mulch around the base provides insulation against freezing temperatures and helps ensure the plant’s return the following spring.