When can I divide garden phlox?
Garden phlox (Phlox paniculata) can be divided in spring or late summer/early fall. In spring, dig up the plants just as new growth begins to appear. Divide each clump into sections with a sharp knife. Each division should contain at least 2 or 3 shoots and a portion of the root system. Replant the divisions immediately. Keep the newly divided perennials well watered through spring and summer. Late summer/early fall (mid-August through September) is also a suitable time to divide garden phlox. Dig up the entire plant, divide the clump into sections, and replant immediately. Plants divided in late summer/early fall should be mulched in late fall. A 4- to 6-inch-layer of straw, pine needles, or similar material should prevent repeated freezing and thawing of the soil that could heave late summer/early fall planted divisions out of the ground and cause severe damage. Remove the mulch in early spring.