A tree peony (Paeonia suffruticosa) is one of the few species of peony that has a woody stem. It can grow up to five feet tall and produces many blooms during late summer. Peonies don't grow true from seed, so you may need to propagate them by crown division if you wish to retain the characteristics of a prize plant.
Prepare the tree peony. Cut the foliage from a mature tree peony in late August or early September. Water the plant in early fall if the ground is dry. Allow the water to soak into the soil overnight before dividing the plant.
Dig the tree peony out of the ground with a spade. Ensure that you get as much of the extensive root system as possible without damaging the crown. Wash the roots thoroughly and leave the plant in the shade for a few hours to soften it.
Cut the plant into divisions with a clean sharp knife. Place the plant on a work bench and make the first cut through the crown. Each division should have at least three crown buds if possible. You may need to trim the roots to a length of six to eight inches if they're excessively long in order to make the cutting process easier.
Store the tree peony divisions. Fill a plastic bag with peat moss for each division and place each division in a plastic bag. You can keep the bags for several days if necessary so long as they remain at a stable temperature.
Plant the tree peony divisions in their new locations so the crown buds are under less that two inches of soil. Apply a layer of mulch during the winter and fertilizer in the spring. The divisions may bloom in the first year.