When should I divide my perennials?
The best time to divide perennials varies with the different plant species. Early spring (just as new growth begins to appear) is the best time to divide aster, chrysanthemum, hosta, bee balm, sedum, yarrow, obedient plant, and ornamental grasses. Bearded iris should be divided in July or August. Late summer/early fall is the best time to divide peonies. Daylily, garden phlox, and coreopsis can be successfully divided in early spring and late summer/early fall.