Plant bare root peonies in the fall, the optimal planting season. Planting in October–November helps roots form before winter. You can transplant potted peony fall or spring.
Dig a 15 x 15-inch hole and fill with spaded dirt. Peony roots can be placed downward at any angle with the buds pointing up. The roots should be near the surface with one to two inches of soil covering the eyes.
Water peonies thoroughly upon planting and during dry weather in the first year. In hot summers, peonies need watering every few weeks but are drought-tolerant once established.
Early spring fertilizer: 10-20-20. Fertilize post-bloom. Deadhead spent flowers to enhance blooming. Peony stems should be cut to ground level in late October for garden cleanup. Avoid composting peony leaves and stems.
Mulching is not necessary in the Northwest, although cold-weather gardeners may do so for protection and remove it in spring. Hidden roots from mulch, tree shade, crowding, or nitrogen misuse may cause sagging peonies.