While some perennial flowers are easy to transplant, getting the best result is primarily a matter of timing. Knowing the right season to transplant a perennial flower will both lessen root shock, thus improving the chances of a plant surviving, and do the least amount of damage to a plant’s ability to flower. The best time to transplant is also the best time to divide your perennial flowers. Move divisions to other parts of the garden, or share them with friends.
Perhaps a tree is creating more shade than it used to, or perhaps a tree has been removed and a previously shady site is now in full sun. Perennial flowers can suffer when their light is changed drastically, and transplanting may be the only way to remedy the situation. Clumps of perennials can become bare in the center and flowering can diminish as they mature, telling you it’s time to divide. Don’t wait until the plant’s appearance is beginning to suffer; dividing perennials when they’re about three times the size they were initially will keep them going strong.
Spring and fall are the best times to transplant perennials, when days are cooler and high temperatures won’t put additional stress on the plants. Transplant spring blooming perennials in fall so that they’ll have ample time to recover before putting out flowers. Summer and fall blooming flowers are best moved in spring, giving them time to adjust to their new location before having to exert excess energy on blooms. If you must transplant in the heat of summer, take additional, almost obsessive care with watering to account for the additional stress. Whatever the season, pick cool, overcast days for transplanting.
Starting several inches out to avoid breaking roots, dig around the perimeter of your perennial and then lift it from the ground. If you’re dividing, use a sharp spade or knife to cut the clump into sections, leaving several stems or buds and ample roots per section. It’s best if you have already prepared a site for your transplant, but you can store it for a while in a shady spot as long as roots are covered and kept moist.