Divisions
Propagation by division is cutting or breaking up a group of suckers or a crown or clump into smaller segments. It is important that each plant segment has a bud or it will not propagate. Most perennials benefit from division as they get older and begin to lose vigor, plus you get more plants to spread around the garden or share with friends. While there are different techniques for dividing perennials, the general rules are the same.
Divide fall-flowering perennials in spring and spring-and summer-flowering perennials in fall. For fall division, plan to do it early in the season as the plants will need 4-6 weeks to become established before the ground freezes. In the spring, divide early. Plants will benefit from the cool, wet weather and be well established before the heat of the summer kicks in.
Two or three days before dividing a plant, water it thoroughly — this will help reduce the stress of division — then cut the plant back so it doesn’t lose too much moisture.
Dig all the way around the perimeter of the plant and gently pull it out of the ground. If you find a huge root ball that you can’t lift, go ahead and cut it through the middle with your shovel. If the plant has a spreading root system, you can probably just pull it apart. Plants that have rhizomes (horizontal, underground stems), can be divided with a sharp knife.
Place the plant segments into a bucket of water right away so there isn’t a chance for them to dry out. While the plants are soaking, dig a hole at least as deep as the plant was originally set. Add peat moss, organic compost or aged chicken manure to give the plant a little edge as it gets established.
Settle the plant segment into the hole and fill with amended soil. Water well. Adding a thick layer of mulch will help the new plant through its first winter, but be sure to pull away some of the mulch in the spring to allow the soil to warm.