Perennials add seasonal color, come back every year, and because perennials are so easy to divide, you always get a great return on the money you invest in their purchase.
After two or three years in the ground, perennials are ready to be divided into smaller clumps. Besides the fact that they grow in size and provide an inexpensive way to add color to your landscape (or even swap with friends), dividing is a good practice that keeps plants healthy. As perennials grow, they may become too dense and crowded for their current space. The plant may become too large and begin to break open or even die off in the middle. Perennial division solves these problems.
Fall is an excellent time for division. The soil temperatures are cooler, rain is more abundant, and daytime temperatures do not cause as much stress on the plant. In addition, it is always a good idea to trim the foliage back by half or more to allow the plant to concentrate its energy into root production. Plus, by cutting your perennials in the fall you will not lose out on their seasonal color.
Steps for dividing perennials:
Because the plant is about to go into dormancy, you will not see an abundance of new growth in the fall. The springtime is another story... your garden will be bursting with healthy, beautiful plants!