Spring is a good time to divide fall-flowering perennials. Do this when the flowers get smaller, the center of the plant dies, or the plant outgrows its space.
A good rule for finding plants that divide well is to look for those that have more than one shoot coming out of the soil.
Dig around the plant, lift the clump out of the ground, and break it into sections. Larger sections will re-establish themselves more quickly than smaller sections.
A good way to divide a clump is to use two spading forks. Insert the forks back to back in the clump. Push the handles toward each other and the clump will come apart with minimal damage to the roots. Discard the center, or old roots, and transplant only the new, strong growth from the clump’s outer edges.
Keep the clumps moist until you are ready to plant them in prepared soil