Chrysanthemums, often called mums, are popular fall-blooming plants that are perennial in many regions, meaning they can return year after year. The question of whether these plants can rebloom after being cut back is rooted in two distinct pruning strategies used throughout the growing season. Strategic cutting, paired with proper timing, is the primary method used to manage the plant’s energy and shape, making an extended or secondary bloom possible. This practice directs the plant’s energy toward creating a fuller, more flower-dense structure.
Timing and Technique for Initial Pinching
The first method of cutting back chrysanthemums is “pinching,” performed long before the first flower buds form. Pinching interrupts the plant’s natural tendency toward apical dominance, where the main stem grows tallest and suppresses side shoots. Removing the growing tip redirects the plant’s energy, stimulating the development of lateral branches, which results in a bushier, more compact plant with a higher number of blooms overall.
Initial cutting back should begin when the chrysanthemum reaches six to eight inches in height, typically in late spring or early summer. The technique involves removing the top half-inch to one inch of new growth on each stem, using the thumb and forefinger or clean pruning shears. This process is repeated every two to four weeks throughout the early growing season as new side shoots reach four to six inches in length.
The timing of the final pinch is important, as late-season pruning removes the buds meant for the main autumn display. Gardeners should cease all pinching by mid-summer, generally no later than the Fourth of July or mid-July. Stopping the pinching allows the plant to transition into its bud-setting phase, which is triggered by shortening day length.
Stimulating a Second Bloom Through Deadheading
Once the plant produces its primary flush of flowers in the fall, deadheading is used to encourage further flowering. Deadheading involves the selective removal of spent or faded blooms, which stimulates a potential secondary display. Removing the withered flower heads prevents the plant from putting energy into developing seeds, allowing it to redirect resources toward producing new flowers.
To deadhead correctly, remove the entire flower head, making the cut just above the first set of healthy leaves or a leaf node below the spent bloom. This precise cut ensures the remaining stem is hidden within the foliage canopy and encourages new growth from that point. While this secondary bloom will likely be less robust than the first, it can significantly extend the color display until the first hard frost.
Aggressive Shearing
For a more aggressive second bloom, particularly in warmer climates, a light shearing of the entire plant can be performed after the first major flush of flowers fades. This method involves cutting the plant back by about one-third of its height, which prompts a fresh wave of growth. This shearing must be done with enough time remaining in the season for new buds to mature, usually with a cutoff date in late September, to avoid forcing tender new growth just before a killing frost.
Environmental Needs for Repeat Flowering
The plant requires specific environmental support to successfully recover and produce a repeat bloom. Chrysanthemums are photoperiodic, meaning they require full sun (at least six hours of direct sunlight daily) to generate the energy needed for both vegetative growth and flower production. Insufficient light results in weak, spindly stems and sparse flowering.
Consistent moisture is necessary, especially immediately following any cutting, as the new growth requires water to develop. The soil should be well-draining to prevent root rot, and watering should be done at the soil level to keep the foliage dry and reduce the risk of fungal disease. Following the initial blooming period, a switch in fertilization strategy can help fuel the secondary growth.
A low-nitrogen, balanced fertilizer can be applied after the first flowers have faded to support the development of new buds without encouraging excessive leafy growth. Proper environmental care ensures the plant has the fuel necessary to respond to the deadheading action and deliver an extended season of color.