Transplant in the fall. When the leaves start to turn brown and fall off, the plant is dormant and ready. Visually draw a line around the plant with the leaves on. This will cover the root mass that must be transplanted. It will be considerable on a 3 year old plant. Use a pitchfork or a mulch fork to dig down along the imaginary line and with each trip around the plant use the pitch fork as a fulchrum to help you loosen the root mass. Once you have the tree peony free, use a water hose and wash all of the soil off of the roots. The hole you transplant in must be as big and deep as the root mass. If any of the plant separates from the mother plant, you can transplant it and it will grow into a new plant. Don't be surprised if the TP is angry and doesn't perform the first year or all the plant above ground dies off only to sprout new scions from the same root mass. It is a big undertaking but can be done. Good luck.
