Place the plants in a bucket of water to wash soil from the roots and rhizomes. Healthy rhizomes should be firm, free of blemishes, and at least one inch in diameter. Unlike many perennials, regular division is not necessary for continued blooming. Keep in mind, however, that peonies often take about three years to return to full bloom and size after division. Taking the time to divide these perennials now will help keep the plants healthy, vigorous, and productive for years to come.