Chrysanthemums, commonly known as mums, are popular flowers recognized for their vibrant autumn display. Naturally, a chrysanthemum plant is programmed for one main flowering period per growing season. However, this single cycle can be significantly extended or encouraged to produce a secondary flush of color through specific gardening practices. The maximum number of blooms seen is a combination of the plant’s inherent biological timing and the care it receives.
The Standard Annual Blooming Cycle
The primary factor determining a chrysanthemum’s flowering schedule is photoperiodism. Mums are classified as obligate short-day plants (SDPs), meaning they require a continuous period of darkness exceeding a specific duration to initiate flower buds. This critical dark period is typically 10 to 12 hours long, depending on the cultivar.
The plant’s leaves sense the shortening days of the year, which naturally provide these longer nights. This biological trigger usually begins in late summer, leading to the main bloom display that peaks in mid to late autumn. Without this photoperiodic signal, the plant remains in its vegetative growth phase, focusing on producing leaves and stems rather than flowers.
In the wild, this single autumn flowering is the plant’s strategy for reproduction before winter. Energy stored throughout the spring and summer is channeled into this one major reproductive effort. This natural mechanism ensures the first and largest display of flowers is generally the only bloom to occur without human manipulation.
Techniques for Encouraging Rebloom
While the natural programming is for a single major event, gardeners can employ techniques to maximize blooms within that season. The most effective method for extending the flower display is deadheading, the process of removing spent or faded flowers. This action disrupts the plant’s reproductive cycle.
The plant’s goal after blooming is to set seed, which signals the end of the flowering phase. Removing the fading blooms prevents the plant from diverting energy into seed production. This saved energy is redirected to secondary buds, encouraging a new, often less dense, flush of flowers.
For this process to be effective, deadheading should begin as soon as the initial flower heads fade, cutting the stem back to a healthy leaf or branch junction. Continued flowering is also supported by adjusting the plant’s nutrient intake. During rebloom, using a fertilizer high in potash (potassium) is beneficial to nourish developing flowers. Avoid fertilizers high in nitrogen during this period, as that nutrient promotes leaf and stem growth at the expense of flower development.
Hardy Versus Florist Varieties
The long-term blooming frequency depends heavily on the specific variety purchased. Chrysanthemums are categorized into two main groups based on their winter survivability and growth habit. Hardy mums, often called garden mums, are perennials that can survive the winter in appropriate climates, typically USDA Hardiness Zones 4 through 9.
These hardy varieties develop underground shoots called stolons, allowing them to establish a robust root system and return year after year. A hardy mum can bloom once every autumn for many years, providing multiple seasonal displays over its lifespan. They are often planted in the spring to establish the necessary root system for winter survival.
In contrast, florist mums, commonly found in stores, are typically treated as annuals. These plants are bred for a single, dense, showy bloom for immediate decorative use. They often have shallow root systems and lack the hardiness to survive a typical winter. For these florist varieties, the answer is generally one time, as they are not intended to return and rebloom.