Chrysanthemums are popular garden additions because they provide a burst of rich color late in the season when many other plants are fading. These plants require a specific pruning regimen throughout the year to ensure they develop a robust, compact shape and produce the maximum number of flowers in the fall. Understanding when and how to cut back these perennials is fundamental to maintaining their health and maximizing their bloom potential.
Understanding Different Types of Mums
The pruning instructions for overwintering apply primarily to “Hardy Mums,” which are perennial garden varieties bred to survive cold temperatures in the ground. These hardy types are distinct from “Florist Mums” often sold as potted decorative plants in the fall. Florist varieties are less cold-tolerant and are generally treated as annuals that will not reliably return the following spring. Hardy garden mums benefit most from a year-round pruning schedule aimed at promoting fall blooming.
Spring and Early Summer Shaping
The first phase of pruning occurs in the spring and early summer, using a technique called “pinching” or “tipping.” This process involves removing the tip of the stem to interrupt the plant’s natural tendency to grow straight up (apical dominance). Pinching encourages the plant to develop lateral branches from the leaf nodes below the cut, leading to a much bushier structure. More branches mean more flower buds will form later in the season.
Begin pinching when the new spring growth reaches a height of about four to six inches. Using your thumb and forefinger or a clean pair of shears, remove the top one to two inches of the stem, snipping just above a set of leaves. This initial pinch will stimulate the first round of side shoots, and the process must be repeated regularly as these new shoots grow.
Continue this shaping every two to four weeks throughout the spring and early summer, repeating the pinch once the new stems have grown another four to six inches. The timing of the final pinch is important because chrysanthemums are photoperiodic, setting buds in response to the shorter daylight hours of late summer. To allow sufficient time for flower buds to develop and bloom fully, stop all pinching by mid-July, or roughly 100 days before you expect the first flowers. Pinching too late will sacrifice the fall bloom display, resulting in fewer or delayed flowers.
Late Fall Cut Back and Winter Preparation
The major cutback should only occur after the plant has completely finished blooming and the first hard frost has caused the foliage to die back. Allowing the foliage to brown signals that the plant’s energy has been redirected to the root system for winter storage. This timing is important for the plant’s long-term health and survival.
Gardeners in colder regions often choose to leave the dead stems standing over winter to provide extra insulation for the crown and root zone. If you opt for a fall cutback, use sharp shears to reduce the dead stems to a height of about four to six inches above the ground. This remaining stalk, often called a “stool,” helps mark the plant’s location and provides a small measure of protection.
Cutting back the dead material in the fall helps to remove overwintering sites for pests and fungal diseases, which can harbor in the spent foliage. Following the cutback, apply a thick layer of winter mulch, such as straw or shredded leaves, to the soil surface around the base of the plant. This mulch does not warm the soil but helps maintain a consistent, cold temperature, preventing freezing and thawing that can push the shallow roots out of the ground.