From our perspective, we do not enjoy being disturbed unnecessarily. Division is a significant shock to our system. Therefore, the ideal time for this procedure is in the early spring, just as our new, green shoots emerge from the crown and are only a few inches tall. At this moment, the soil is workable and moist, and our energy is surging upwards into new growth, which means we can recover from the trauma of being split much more quickly. Alternatively, you can perform this task in the early autumn, after our flowering show is over but while the soil is still warm, giving our roots time to establish before winter's dormancy.
Please be careful. Our root systems, though extensive, are surprisingly brittle. The day before you plan to divide us, give us a deep, thorough watering. This will hydrate our cells, reducing transplant shock, and make the soil easier to work with, allowing you to extract our root ball with minimal damage. Use a sharp, clean spade to dig a wide circle around the crown, giving our outer roots a wide berth. Gently lift the entire clump from the ground, trying to keep the root ball as intact as possible.
Now, you must separate us. You will notice our crown is a dense, woody mass. Do not simply pull us apart with your hands; this will cause excessive tearing and damage. Instead, use a sharp, sterilized knife or even two garden forks placed back-to-back in the center of the clump to gently pry us apart. Your goal is to create new sections, or "divisions." Each division must have at least two to three healthy green shoots (or "eyes" in early spring) and a substantial portion of our creamy-white, healthy roots attached. A division with insufficient roots will struggle to uptake the water and nutrients it needs to survive.
While we are out of the ground, prepare the new planting sites. We delphiniums are heavy feeders and demand excellent drainage to prevent our crowns from rotting. Amend the soil with plenty of well-rotted compost or manure to replenish nutrients. The hole should be wide and deep enough to accommodate our roots without bending or crowding them. Create a small mound of soil in the center of the hole upon which to rest our crown.
Place each division in its prepared hole. It is crucial that our crown—the point where our roots meet our shoots—is planted at the exact same soil level as we were growing before. Planting too deep invites rot, while planting too high exposes our tender crown. Backfill the hole gently, firming the soil around our roots to eliminate air pockets. Water each new transplant deeply and thoroughly to settle the soil around our roots. To help us conserve energy and focus on root establishment, keep the soil consistently moist (but not waterlogged) for the next several weeks. Applying a layer of mulch around our base will help retain that crucial moisture and regulate soil temperature.
