Tree peonies, shrubs that reach up to 5 feet tall, are known for their showy fragrant flowers. Tree peonies may have double, semi-double or single flowers in nearly any colour except blue. Once established, tree peonies are relatively easy to care for and provide many years of enjoyment. Tree peonies may be propagated by grafting, air layering or division, but grafting a tree peony is its most common propagation method.
Select a medium to small tree peony stem with buds, one that won't be too top heavy for grafting. Leave it on the shrub for now; the first step is simply identifying it.
Cut a root from a herbaceous (garden) peony, place it in a glass jar and cover it with a solution of 5 per cent bleach water. Purify the root by allowing it to soak for 25 minutes. Be sure to pick a root that is the same diameter as the tree peony stem. This will serve as the nurse root until the tree peony can establish its own root system.
Remove the root from the bleach water and dab it dry. Cut a v-shape out of the top of the root. Now cut your selected tree peony stem and trim it into a v-shape so that it fits into the v-shape of the cut root.
Fit the stem and root together, and secure them with Parafilm M, which is an adhesive film that will hold the two together, keep water out of the join and permit air circulation.
Fill a flowerpot with moist sphagnum moss and place the grafted cutting in the moss. Keep it in a warm place and water it as needed to keep the roots somewhat moist.
Plant your tree peony outdoors when growth has been established. Bury the plant deeply to encourage the grafted tree peony to develop its own roots. It is best to plant tree peonies in the fall.
It may take up to three years before tree peonies flower. The flowers will grow larger and more plentiful in succeeding years.
It is important to keep water out of the join or else the peony graft will not grow.