Chrysanthemums, often called mums, are classic garden plants whose vibrant, mounding blooms signal the arrival of autumn. Achieving that spectacular, dense display of fall color requires more than simply planting them and waiting. Successfully coaxing a chrysanthemum to produce abundant flowers involves specific, timely interventions that work in harmony with the plant’s natural biology. Understanding the relationship between light exposure, physical shaping, and nutrient delivery will ensure the plant successfully sets buds and delivers a prolific seasonal show.
Understanding the Light Trigger
The chrysanthemum plant is classified as a short-day plant, meaning its flowering is triggered by the length of the uninterrupted dark period. To initiate flower bud formation, the mum requires a dark period of approximately 10 to 12 hours that is not broken by light. This requirement is naturally met in late summer as the nights begin to lengthen.
The presence of any artificial light during this long night period can disrupt the process and prevent blooming entirely. Light from a streetlamp, porch light, or a window can trick the plant into believing the night is too short, halting the transition from vegetative to reproductive growth. Therefore, positioning your mums where they receive total darkness from dusk until dawn is paramount, especially as August approaches and flower buds are preparing to set.
Pinching for Prolific Blooms
The technique of “pinching” is the most effective way to encourage a compact, bushy chrysanthemum that produces dozens of blooms instead of a few tall, spindly stems. Pinching works by removing the apical meristem, which is the primary growth point at the tip of the stem. This removal releases the plant’s natural hormonal dominance, specifically suppressing the growth-regulating auxin, which encourages the side, or lateral, buds to break dormancy and begin growing.
The physical action involves using your thumb and forefinger to remove the top half-inch to one inch of new growth on each stem. This process should begin when the plant is young, typically around six inches tall, and repeated every two to three weeks during the active growing season. The timing of the final pinch is essential, as doing it too late will remove the developing flower buds. Gardeners should stop all pinching activity by mid-summer, typically around the Fourth of July, to allow the plant sufficient time to develop its fall flower buds.
Fueling the Flowers: Soil and Fertilization
Chrysanthemums are considered heavy feeders, requiring a consistent supply of nutrients to support their vigorous growth and massive fall bloom. They perform best in well-draining soil that is rich in organic matter, which helps retain moisture and nutrients. Proper feeding should be adjusted based on the plant’s stage of development.
Vegetative Growth (Spring and Early Summer)
During the vegetative growth phase, a balanced fertilizer is recommended, such as a 20-20-20 NPK formula. This provides the necessary nitrogen for lush foliage and strong stem development, preparing the plant to hold many flowers. Apply this balanced feed every three to four weeks until the plant begins to set buds.
Reproductive Stage (Late Summer)
As the plant transitions to the reproductive stage in late summer, the nutritional needs shift dramatically. It is important to reduce or stop nitrogen application, as too much will promote leafy growth at the expense of flower production. Instead, switch to a bloom-boosting formula high in phosphorus (P) and potassium (K), such as a 4-18-38 blend. This supports bud initiation, flower size, and color vibrancy. Consistent watering is also necessary, especially as buds swell, to prevent stress and ensure the development of large, healthy blooms.