Transplanting perennials allows you to expand your perennial bed. For many gardeners, transplanting is a time of sharing their excess plants with others and collecting a few free plants of your own. According to the University of Utah’s Cooperative Extension, perennials can be transplanted in either spring or fall, but fall is the preferred time for transplanting.
Allow plants to rest for two weeks or more after blooming. This allows the plants to renew the energy expended during blooming. If your perennials bloom late in the fall, it is best to wait until spring to transplant them.
Cut the foliage back to 6 to 8 inches from the ground. This reduces energy demands on the plant and prevents excess moisture loss during transplanting.
Prepare a new site for the transplants before digging them to from the original site to reduce stress on the plants. Choose a location with similar soil, sunlight and moisture to the area where the perennial grows successfully.
Amend the soil with generous amounts of compost or well-rotted manure to improve aeration and promote good drainage. Avoid fertilizer at this time.
Dig up the perennials on a cool day. An overcast or rainy day is ideal. Dig around the clump of flowers with a garden spade or garden fork to loosen the root ball. Slide the blade of the spade beneath the roots and lift to remove the entire clump.
Examine the roots for any signs of disease. Healthy roots are light tan or white. Black or mushy roots indicate disease. Cut away any discolored roots.
Separate roots by teasing them apart, or separate tubers or bulbs by cutting or pulling into sections. Each section should contain two to three shoots of foliage.
Transplant the perennials to the original planting depth in the prepared bed. Cover the roots with soil and firm down with your hands to remove air pockets and secure the plant.
Water thoroughly to saturate the soil to the root level. Newly transplanted plants suffer some root loss and require plenty of water.
Check the soil daily and keep soil moist for the first week or two to speed root formation.
Mulch newly transplanted perennials with two to three inches of hay or leaves for winter protection. This prevents the roots from heaving as the soil freezes and thaws during the winter.
Remove mulch in the spring when the weather warms and new growth appears. An application of balanced fertilizer may be applied in the spring and again just before blooming.
University of Illinois Extension: Revive the Perennial Garden
University of Utah’s Cooperative Extension