Tree peonies can be propagated by taking cuttings of their stems and preparing them for rooting and then planting. Unlike their cousins the herbaceous peonies whose foliage dies back yearly, tree peonies are treated like shrubs or small trees for purposes of creating offspring. According to Ken Druse in "Making More Plants," take cuttings in fall or winter after leaves have died back and before they begin to develop new buds in spring.
Use clean, sharp pruning shears to snip off woody stems that contain at least a few buds; eight to 10 inches long not counting the terminal end of the branch as this will be cut off. Trim the bottom just above a bud that will remain on the tree so that you have a smooth, straight end.
Cut off the terminal end of the stem. This is where multiple buds may be situated at the very tip. Trim it straight across with the shears
Hold the stem flat against a cutting surface and use the razor blade to make the bottom of each stem flat and round. Take note of which end of the stems are the bottom as it does make a difference which direction they are planted in. If necessary, tie a colourful string to mark the top of each stem.
Dip each cutting bottom into rooting hormone for the length of time specified by the label on the product.
Fill a planting tray or small wooden crate with sand and place the cuttings on top of the sand horizontally per Ken Druse in "Making More Plants." Cover the cuttings with additional sand and water the box until it is barely damp.
Store the cuttings in a cool room at around 4.44 degrees Celsius. According to Ken Druse in "Making More Plants" that is the ideal temperature for creation of the calluses that will form at the cutting bottoms. An ideal place would be an unheated laundry room or basement. Store the box over winter.
Check the cuttings in spring for calluses. The calluses will simply appear to be swollen growths at the base. Transfer the cuttings to potting soil and plant them callus-end down at a depth of a third to a half the height of the cutting per Ken Druse. This can be outdoors or in a greenhouse setting.
Keep the cuttings in a shaded area or use a screen to protect them from direct sunlight.
Allow the cuttings to develop roots over the warm weather months without disturbing them other than to water when the soil is dry. Dig them up at the earliest in the fall and transfer them to their new home.
- "Making More Plants;" Ken Druse; 2000