Scarify the seeds with a file to have them soak up the water better, soak the seeds overnight in water. Place the tree peony seeds in a 1-quart plastic bag filled with 1 cup of moistened perlite. Seal the bag, and place it in a moderately warm, dark area of your house such as inside a kitchen cupboard.
Check the seeds every day. Remoisten the perlite with a spray bottle whenever it feels nearly dry. Inspect the seeds for the emergence of a single, translucent white root.
Transfer the sprouted tree peony seeds into individual 4-inch starter pots filled with a sterile, soilless growing mix. Poke a hole in the growing mix that is deep enough to accommodate the root.
Moisten the growing mix with a spray bottle after transplanting the seed. Place the pots in a cool area where temperatures stay around 40 Fahrenheit, such as outdoors against a north-facing wall or inside the crisper drawer of a refrigerator.
Keep the tree peony seedlings under cool conditions for 10 to 12 weeks. Regularly moisten the growing mix so that it never completely dries out. Cover the pots with a plastic bag if the growing mix tends to dry out quickly. After the cooling time, transfer the tree peony seedlings to a very bright location where temperatures stay around 60 F, such as indoors near a north-facing window or outdoors under a shaded porch.
Grow the tree peony seedlings under bright, cool conditions for their first summer. Water them only when the top 2 inches of soil dries out. Acclimate them to partial sun exposure for two weeks before transplanting them.
Transplant the tree peonies into the garden in fall after the foliage dies back. Choose a bed with dappled shade and moist, fast-draining soil. Spread a 3-inch-thick layer of mulch around each plant to protect the roots.
Hardy zone 3-8, great cut flower