Dividing Spring and Summer Blooming Perennials
Late summer through early fall is a great time to dig and divide overgrown spring and summer blooming perennials.
The soil is warm, air much cooler and the plants will have time to adjust to their new location before winter.
Dig and divide plants that have stopped blooming, flopped over, or have a dead center. Use a sharp spade shovel or garden fork to dig up the plant. Cut the clump into 2, 4 or more pieces. Remove the dead center and add it to the compost pile.
Some gardeners use two garden forks back to back to pry the clump apart. I prefer a sharp linoleum knife or drywall saw. Though some fleshy rooted plants like daylilies and willow amsonia may require a hatchet or machete.
You can replant one piece back in the original location after amending the soil with compost. Use other divisions in other areas or share with friends.
A bit more information: The old adage “Divide spring blooming perennials in fall, fall blooming perennials in spring and summer blooming perennials in spring or fall” is a good guideline. But experienced gardeners have all stretched these limits. Sometimes necessity and your schedule determine when you divide perennials. Proper post-transplant care will give your plants the best chance of survival no matter when you divide them.