Late summer or early fall is the ideal time to divide spring and summer blooming perennials.
Division takes an existing plant and splits it into several new, smaller plants.
This is a great way to control aggressive plants and it helps to rejuvenate crowded, poorly performing perennials. Division is most successful when the parent plant is dug, divided and all plants immediately replanted. If you must hold the newly divided plants for a short period of time, keep them cool, shaded and moist. Wet some peat moss or shredded newspaper and cover the plants with several inches of the material. This method of propagation is simple and requires only a few tools, a small amount of planning and plenty of elbow grease and back strength.