From my perspective as a Paeonia lactiflora, the most critical factor for a successful division is timing, which is intrinsically linked to my annual growth cycle. I enter a period of dormancy in the late autumn, typically after the first frost has blackened my foliage. This is a signal that my metabolic activities are slowing down, and energy is being withdrawn from my leaves and stems down into my root system and the "eyes," or dormant buds, for winter storage. Dividing me at this time, while I am asleep, causes the least amount of shock. The cool soil temperatures help prevent the exposed, fleshy roots from rotting and allow me to focus all my energy on establishing new roots before the demands of spring growth begin. Attempting to divide me in the spring or summer is highly detrimental, as it disrupts my active growth, flowering, and nutrient storage processes, often leading to my decline or death.
Before you begin, it is essential to understand my subterranean architecture. I do not grow from a bulb or a single taproot. Instead, I possess a dense, woody crown from which thick, fleshy, tuberous roots radiate. These roots are my nutrient reservoirs, packed with the carbohydrates I need to fuel next season's spectacular blooms. The most vital parts of my above-ground structure are the "eyes." These are not roots but the pink, red, or white buds clustered on the crown, just above the roots. Each eye is a potential stem for the coming year. A successful division must ensure that each separated section has an adequate number of these eyes (typically 3-5) and a sufficient mass of healthy roots to support their growth. Without eyes, a root division will not produce new shoots.
The process of dividing me must be undertaken with care. First, carefully dig a wide circle around my base, staying well away from the crown to avoid slicing through my valuable roots. Gently lift the entire root mass from the ground and wash off the soil with a gentle spray of water. This allows you to see the crown's structure and the eyes clearly. Using a sharp, sterilized knife, you will need to cut my tough crown into sections. Aim for clean cuts, not ragged breaks. Each new division should have at least three to five well-developed eyes and a generous portion of healthy, fleshy roots attached. You may need to remove any old, hollow, or diseased parts of the crown, which is beneficial for my long-term health.
Once divided, my new sections are vulnerable and require specific conditions to thrive. The planting hole is crucial. It should be wide and deep enough to accommodate my roots without bending them. The most common mistake is planting me too deeply. My eyes must be no more than 1 to 2 inches below the soil surface in colder climates, and even shallower in warmer ones. If buried too deep, I will struggle to emerge and will likely refuse to bloom for years. Amend the soil with compost to provide nutrients and ensure excellent drainage, as my fleshy roots are highly susceptible to rot in waterlogged conditions. After planting, water me thoroughly to settle the soil around the roots. A layer of mulch can be applied to protect me from winter temperature fluctuations, but ensure it is not piled directly on top of the crown where the eyes are located.