Chrysanthemums, commonly known as mums, are a favorite for container gardening, offering a burst of vibrant color, especially in the autumn. Most mums purchased from nurseries are intensely root-bound, meaning the roots have filled their small pots. This condition severely limits the plant’s ability to absorb water and nutrients. Repotting into a larger container with fresh potting mix is necessary for ensuring continued health, robust growth, and prolonged flowering.
Preparing for the Repotting Process
The preparation for repotting involves timing and materials to minimize the plant’s stress. The optimal time for this procedure is typically in early spring when new growth emerges, giving the plant a full season to establish itself before blooming. If you purchase a fall-blooming mum, repotting it immediately after bringing it home is recommended to address the root-bound condition.
Selecting the correct container size is important for healthy root development. The new pot should be approximately two to four inches larger in diameter and depth than the original one, providing ample room for the shallow root system to spread. A high-quality, well-draining potting mix, ideally one based on peat or bark, will support moisture retention without becoming waterlogged. To reduce the risk of transplant shock, thoroughly water the mum 12 to 24 hours before you plan to repot it.
Step-by-Step Repotting Instructions
Repotting begins with carefully removing the mum from its original container. Place one hand over the soil surface, gently cradling the plant’s base, then invert the pot and tap the rim or base to loosen the root ball. Inspecting the exposed root mass is important, as most store-bought mums will show a dense, circling pattern of roots, a sign of being root-bound.
To encourage outward growth into the new soil, gently disrupt the tightly wound root ball by teasing the outer roots apart with your fingers. If the roots are severely matted and circling, use a clean knife or scissors to make several shallow, vertical cuts along the sides of the root ball. This scoring action interrupts the circling pattern, signaling the roots to grow straight out once placed in the new medium.
Place a layer of fresh potting mix in the new container, adjusting the amount until the top of the mum’s root ball sits about one inch below the rim of the pot. The crown, where the stems emerge from the roots, must remain at the same level as it was in the old pot to prevent smothering the plant. Fill the space around the root ball with the new potting mix, working it gently into all gaps to ensure good root-to-soil contact. Gently firm the soil surface with your hands, avoiding excessive compaction that could impede drainage and root respiration.
Dividing Mature Mums
If you are repotting a large, mature perennial mum in the spring, this is the ideal time to divide the plant to rejuvenate it. After removing the plant, use a sharp, clean spade or knife to separate the outermost, healthiest sections, discarding the older, woody central portion of the root mass. Repot each division into its own appropriately sized container, following the same steps for root preparation and planting depth.
Post-Repotting Care
Immediate care following repotting is essential for the mum’s swift recovery and establishment. The first step is a deep, generous watering until water flows freely from the drainage holes. This initial soak settles the fresh soil around the roots and eliminates any air pockets that could cause root desiccation.
For the first few days, place the newly repotted mum in a location that receives bright, indirect light or partial shade to allow it to recover from the stress of transplanting. After this brief recovery period, gradually transition the plant back into a spot that provides a minimum of six hours of direct sunlight daily, which is necessary for abundant blooming. Monitor the soil moisture daily, watering whenever the top two inches of soil feel dry to the touch. Avoid applying fertilizer for two to four weeks, giving the roots time to heal and begin active growth before introducing additional nutrients.