Whether a mum (chrysanthemum) will survive the winter is a common question for gardeners as autumn ends. These popular flowering plants, prized for their vibrant, late-season color, are often purchased in full bloom, leading to confusion about their long-term life cycle. Survival depends entirely on the specific variety purchased and the preparation taken before the ground freezes. Understanding the difference between the types of mums available determines whether the plant is a perennial intended to return or an annual.
Identifying Your Mum: Hardy vs. Tender Varieties
A chrysanthemum’s winter survival rests on its genetic makeup, categorizing it into two main groups. The first is the garden mum, a hardy, perennial variety bred to withstand cold temperatures and return annually. These varieties develop a robust root system capable of surviving winter dormancy in the ground, often tolerating temperatures down to USDA Hardiness Zone 5, or sometimes colder with protection. Garden mums tend to have a more sprawling growth habit and smaller, plentiful flowers compared to their counterparts.
The second type is the florist mum (or pot mum), which is a tender variety best treated as an annual. These chrysanthemums are cultivated for their dense, uniform shape and large, showy flowers, making them ideal for seasonal displays in containers. Florist mums are usually grown in greenhouses; their shallow, tightly bound root systems lack the energy reserves and cold tolerance needed to survive a harsh winter.
Preparing Perennial Mums for Winter Dormancy
Hardy garden mums must be properly prepared to enter dormancy, a state of reduced metabolic activity, to survive the winter. Preparation begins after the first hard frost, which signals the plant to slow down its growth and conserve energy. Gardeners should prune the dead or frosted stems, cutting them back to a height of about four to six inches above the soil line. Leaving some stem length protects the crown (the plant’s base where new growth emerges) and provides a structure to trap insulating snow.
Deep watering before the ground freezes ensures the roots are adequately hydrated before winter. Once the ground is frozen solid, a thick layer of insulating mulch should be applied over the crown. This mulch, ideally four to six inches of straw, shredded leaves, or evergreen boughs, is not meant to keep the ground warm but to maintain a consistently cold temperature. The mulch layer prevents the plant from being damaged by freeze-thaw cycles, which can cause the shallow root crown to heave out of the soil and be exposed to drying winds and severe cold.
Post-Winter Recovery and Spring Maintenance
Bringing a hardy mum out of dormancy begins in the spring once the danger of the last hard frost has passed. The heavy winter mulch layer should be carefully pulled back or removed to allow new growth to emerge and to prevent the crown from rotting in moist conditions. Successful overwintering is confirmed by the appearance of small, green shoots emerging from the base of the plant, known as the crown.
When new stems reach about six inches, begin a technique called “pinching back.” This involves removing the top inch or two of the new growth, which encourages the plant to branch out laterally rather than growing tall and spindly. Repeating this pinching process every few weeks until early July promotes a denser, bushier plant, resulting in a greater number of flowers and a more appealing dome shape in the fall. Providing a balanced fertilizer in early spring helps replenish energy stores used during dormancy and supports vigorous new growth.