Chrysanthemums (mums) are a beloved fixture in the autumn garden, requiring routine care to maintain their health. A fundamental practice for ensuring these hardy flowers thrive is periodic division. This process prevents the plant from becoming overly dense and allows you to multiply your existing stock, keeping your garden full of healthy blooms. Understanding the correct timing for this maintenance is key to a successful division.
Why Dividing Mums Is Essential
Mums tend to form dense clumps over time, typically within three to five years. This clumping habit leads to overcrowding, causing root systems to compete intensely for limited soil nutrients and moisture. Overcrowding also reduces air circulation around the plant’s base, which can encourage fungal diseases.
As the plant matures, the center of the clump often becomes woody and unproductive, resulting in fewer flowers and sparser foliage. Dividing the plant effectively rejuvenates it by removing this old core. This practice ensures that only the young, healthy, outer portions of the plant are kept, leading to robust growth and abundant flowering in the fall.
Identifying the Optimal Time for Division
The optimal time for dividing chrysanthemums is in the early spring, just as the new shoots begin to emerge from the soil. This window, when new growth is between one and three inches tall, allows the plant to focus its energy on establishing new roots before the summer heat arrives. Spring division provides the young plants with a full growing season to develop a substantial root system, necessary for surviving the following winter and producing flowers later that year.
Dividing mums in the fall is discouraged because the plant’s energy is focused on flowering rather than root development. Fall-divided plants may not establish a strong root network before the ground freezes, making them susceptible to winterkill. By dividing in the spring, you maximize the plant’s ability to recover from the disturbance and anchor itself securely in the soil.
Step-by-Step Guide to Dividing Mums
Begin by carefully digging around the clump with a garden spade, working six to eight inches away from the center to minimize root damage. Once the root ball is loose, lift the plant from the soil and shake off excess dirt to expose the root structure. This allows you to clearly identify the healthy, vigorous new growth ringing the perimeter.
Separate the clump, retaining the young sections while discarding the old, woody center. Use a sharp knife or the edge of your spade to cut the root mass into smaller sections, ensuring each new division has several healthy shoots and a substantial portion of roots attached. The divisions are then ready for replanting.
Ensuring Success After Replanting
Replant the young divisions immediately at the same depth they were growing previously. The crown, where the stem meets the root, should sit right at the soil surface, not buried too deep. Ensure new divisions are planted eighteen to twenty-four inches apart to allow for good air circulation as they mature.
Immediately after replanting, water the divisions thoroughly to settle the soil around the newly cut roots and eliminate air pockets. Maintaining consistently moist soil for the first few weeks is essential for encouraging rapid root establishment. Applying a light, two-inch layer of organic mulch around the new plants will help regulate soil temperature and conserve moisture.