Peonies are some of the showiest and best-loved flowering plants in the home garden. The plants can live up to 50-70 years, so a bit of care when they first go into the ground will be well rewarded with many years of fabulous blossoms. First-time growers may wonder when to plant peony. All varieties of peony should be planted in the early fall, with September-October being ideal. This gives them the winter to develop a strong root system that will support spring growth and flower production.
Sun and Shade
Also, take time to determine where the peonies will do best in your garden. Plenty of air circulation is probably the most important factor, as peonies are subject to a fungal disease called botrytis. Fungal diseases are encouraged by damp, crowded conditions and excessive shade. The peony should get at least a half-day of sun, and full sun is usually preferable. Somewhat paradoxically, peonies that are grown in warmer climates benefit from a little more shade. Good drainage is also essential.
Cold climate zones
Most peonies do best in the colder climate zones, USDA Hardiness Zones 4-7, but they can also do well in Zones 8-9 with a little special consideration. Use either bare roots or nursery-grown container plants. It is best to prepare soil ahead of time to allow it to settle before introducing the plants.
Types of Soil
Several days before planting peonies, dig deeply to loosen the soil. This is extremely important. The roots cannot grow well in compacted soil. Work in well-rotted compost. However, keep in mind that peonies like a slightly acid soil (6.5-7) so if you have somewhat alkaline soil, use azalea or rhododendron soil mixture instead. This is already acidic. Once you have added soil conditioner and have a nice, crumbly texture, let the soil settle.
If planting bare bulbs, take care not to put them too deep. The crown should be about 2″ below the surface for cold climates, and a bit less in warmer climates.