Divide when plants become overcrowded, bloom size begins to diminish or plants lose their vigor. Most perennials can be divided every 3–5 years.
- Divide late summer and fall-blooming varieties in spring, and spring-blooming varieties in fall.
- When plants are dormant in spring or fall, dig clumps from the ground and with a sharp knife or spade, cut into good sized divisions, each with several growing points and plenty of roots.
- Remove any dead or unhealthy plant parts and cut back stems.
- Replant one division where the plant was originally and plant the extra divisions elsewhere in your garden or give them away to gardening friends.
- Plant the divisions immediately, or as soon as possible, and water well.