September is a perfect time to divide and propagate perennials. Many plants, such as daylilies, coneflowers, black-eyed susans, and hostas, can be divided once they have been in the ground for 3 years or more. Division is one of the quickest ways to propagate perennials. This technique can also be used on containerized plants bought in garden centers, as long as the plants are well-rooted. Some nursery growers often put more than one actual plant per pot in order to make the plant sell faster. This is to the gardener’s advantage, because one purchased plant may then be divided into 2 or 3 plants.
The easiest technique is to simply use a sharp shovel, saw, or knife to literally cut up the root ball. Another method for division that will preserve the root system is to place the clump into water to remove the excess soil. This allows the roots to be loosened, and individual plants may be easily pulled apart. Perennials are best divided during the cooler spring or fall months. For more information on dividing perennials please see, HGIC 1150, Dividing Perennials.