Chrysanthemums, commonly called mums, are popular garden plants valued for their vibrant fall blooms. To remain healthy and produce consistent blooms, these perennials often require periodic division and transplanting every two to three years. This process rejuvenates aging plants and prevents the center from becoming woody and unproductive. The timing of the move is crucial for successful long-term establishment.
Optimal Timing for Transplanting
The best time to transplant chrysanthemums is in the early spring, just as new shoots emerge from the base of the plant. This timing allows the plant to focus energy on root development throughout the growing season before the stress of fall blooming. Spring transplanting provides several months of warm weather to establish a robust root system, which is essential for long-term survival and abundant flowering.
While spring is preferred, fall transplanting is possible but requires caution. The move must be completed at least six weeks before the date of the first anticipated hard frost in your region. This window allows the shallow root system time to anchor itself and minimizes the risk of frost heave, where the freezing and thawing of the soil pushes the plant out of the ground.
Mums also indicate when they need division, regardless of the calendar. Signs include a woody, non-productive center, decreased bloom count, or when the overall clump appears crowded and less vigorous. Dividing the plant when these indicators appear ensures the new sections remain healthy and maintain their flowering capacity.
Preparing the Plant and New Site
Preparation for the move should begin a couple of weeks before the actual transplanting date. If the mum still has significant old growth from the previous season, prune the stems down to approximately 4 to 6 inches above the soil line. Pruning helps the plant direct energy toward root repair and new growth rather than maintaining unnecessary foliage after the move.
The day before transplanting, thoroughly water the chrysanthemum at its base until the entire root ball is saturated. A well-hydrated plant is more resilient and helps ensure the soil adheres to the roots during the digging process, minimizing root disturbance.
Prepare the new planting site, ensuring it receives at least six hours of direct sunlight daily, as mums thrive in full sun. Dig the new hole to be roughly twice the width of the root ball but no deeper than the existing planting depth. Improving the soil within the hole with compost or other organic material enhances drainage and provides beneficial nutrients for the newly establishing roots.
Executing the Transplant Process
When physically moving the plant, use a sharp spade to dig a wide circle around the perimeter of the existing clump to secure a large, intact root ball. The shallow root system of the chrysanthemum makes it relatively easy to lift the entire plant out of the ground. Gently shake off excess soil to better expose the roots and prepare the plant for division.
If the plant is mature and requires division, use a sharp knife or spade to cut the clump into smaller sections. Each new division should have several healthy shoots and a substantial portion of the root system attached. Discard the old, woody center of the original plant, as this section is past its prime and will not produce vigorous new growth.
Set the newly divided section into the prepared hole so that the plant’s crown—where the stems meet the roots—is level with the surrounding soil line. Planting too deeply can lead to crown rot. Backfill the hole gently with the amended soil, lightly tamping the area to remove large air pockets.
Post-Transplant Care
Immediate and thorough watering is the most important step immediately following the transplant to settle the soil around the roots and prevent transplant shock. Maintain consistent moisture in the soil for the first few weeks, especially during periods of warmer weather, but avoid creating a waterlogged environment that could suffocate the roots.
Apply a 2- to 3-inch layer of organic mulch around the base of the transplanted mum to help retain soil moisture and regulate soil temperature. Be careful to keep the mulch away from the plant’s crown to allow for proper air circulation, which prevents moisture buildup and potential rotting.
Monitor the plant closely for signs of transplant shock, which can manifest as wilting, yellowing leaves, or stunted growth. If the plant shows signs of severe wilting during the hottest part of the day, providing temporary shade for the first few days can reduce stress. Avoid applying heavy fertilizer immediately, as the plant needs to focus energy on root recovery before taking up strong nutrients.
To encourage a bushier growth habit and a greater number of flowers in the fall, you may begin pinching the tips of the new growth. Pinching involves removing the top half-inch to inch of the soft new growth, and it should be done periodically until mid-summer to promote lateral branching.