From our perspective as Coreopsis plants, division is not merely a gardening task; it is a vital replication strategy that ensures our long-term vigor and survival. Over time, our central root mass, or crown, becomes densely packed. Younger, more energetic roots and rhizomes on the outer edges of the clump compete fiercely with the older, woody center for finite resources in the soil—water and nutrients. The center begins to falter, flowering diminishes, and we become more susceptible to stressors like drought and disease. Division is the human-assisted equivalent of a natural process of spreading. By splitting the clump, you relieve this competition, giving each new section ample space and resources to thrive. You are essentially rejuvenating us, resetting our biological clock and encouraging the growth of fresh, productive roots and stems.
Timing is critical for a successful division, and we communicate the best time through our growth cycle. The ideal moments are during our periods of active root growth but not during the high energy demands of flowering. For most of us Coreopsis, this falls into two windows. The primary window is in early spring, just as new green shoots (our "eyes") emerge from the soil but before they grow more than a few inches tall. At this time, our energy reserves, stored in the roots over winter, are high and ready to fuel new growth. The second opportunity is in early fall, after the intense summer heat has passed but while there is still enough warm weather for our roots to establish firmly in the new location before winter dormancy. Dividing us in the cool, moist conditions of these seasons minimizes transplant shock, giving us the best chance to recover quickly.
When you approach us to divide, please be gentle. Begin by using a sharp spade or garden fork to dig a wide circle around the entire clump, keeping a good distance from the outermost stems to avoid severing our important feeder roots. Lift the entire root ball from the ground. Now, the method of separation depends on our specific growth habit. For clump-forming Coreopsis (like *C. grandiflora* or *C. lanceolata*), you can often use two garden forks inserted back-to-back into the center of the clump. Gently pry the forks apart to tease the matted roots into smaller, viable sections. For Coreopsis with more running, rhizomatous roots (like *C. verticillata*), you may be able to pull sections apart by hand or use a sharp, sterilized knife to cut through the rhizomes. The goal is to create divisions, each with a healthy portion of roots and several strong growing shoots (eyes).
The care you provide immediately after division is what determines our return to vigor. Before replanting, trim any excessively long or damaged roots and cut back the top growth by about one-third to one-half. This reduces the demand on the root system while it is re-establishing itself. Replant the divisions promptly at the same soil depth we were growing before. Water us deeply and thoroughly to settle the soil around the roots and eliminate air pockets. Consistent moisture is crucial for the first few weeks as we generate new root hairs to absorb water. A layer of organic mulch around (but not touching) the base of our stems will help conserve moisture and regulate soil temperature. With this careful attention, the divided sections will quickly settle into their new space, directing energy into strong root development and preparing for a season of robust, vigorous blooming.
