Fern-leaf peonies (Paeonia tenuifolia) have divided, fern-like leaves topped with dark red single or double flowers. This variety of peony commonly grows only 18 inches tall. It blooms earlier than normal peonies and is difficult to propagate, which makes it more expensive. The fern-leaf peony will live 50 years or more, so plant it in a permanent location. Always choose peony roots with three to five eyes or buds, since they flower sooner than roots with two or less eyes. It may take up to three years for the fern-leaf peony to flower.
Plant your fern-leaf peonies in the fall, from the beginning of September until the end of October. Remove grass and weeds from the planting site. Loosen the soil in the peony bed to the depth of 12 to 24 inches with a shovel.
Dig a hole 12 to 18 inches deep and 12 inches across. Create a mound of soil in the bottom of the hole. Set the fern-leaf peony in the hole and spread its roots around the mound.
Keep the eyes of the fern-leaf peony no deeper than 1 inch below the soil level. Adjust the soil mound to raise or lower the planting depth. If planted too deeply, the fern-leaf peony will take longer to bloom than normal.
Press the soil down around the roots as you replace the soil in the hole. This will help eliminate air pockets around the roots. Plant the rest of the fern-leaf peonies 24 to 36 inches apart to give them room to expand.
Flood the planting area with lots of water. Let the water soak into the soil and water thoroughly again. Water every 10 to 14 days until the ground freezes and then continue the watering schedule in the spring until the red peony shoots appear.