For me, one of the peony's biggest attractions is its long life. I've heard of herbaceous peonies blooming reliably for more than 50 years, sometimes outliving the gardeners who planted them! But the key to their longevity is the care you take in establishing them.
I've found the ideal time to plant bare root peony tubers is in the fall, just as the first leaves begin to turn. Now the term bare root means that all the soil was removed from around the tuber when the plant was dug from the field. I prefer planting bare root peonies because they are less expensive than container grown plants and by planting them in the fall they will have time to develop a strong root system, ready for robust growth next spring.
Whether you purchase your bare root peonies from a local garden center or through a mail order source the first thing you want to do when you open the package is check that the plant is healthy. The tubers should be fleshy, firm and mold free.
Sometimes bare root plants can dry out during transit so it is a good idea to soak them in a bucket of water for 2 to 4 hours to rehydrate them before planting.
If you cannot plant the tubers right away keep them in their packing material in a cool, dry place, such as a garage, or basement. Warmth and moisture will signal the tubers to start growing so check on them occasionally to be sure they aren't getting moldy or soft. They can be kept this way for about 5 days.
Choose an area that is in full sun with well-drained, slightly acidic soil. And bear in mind that peonies do not respond well to transplanting once they have become established, so select an area where they can remain undisturbed.
Peonies should be planted with the eyes pointing up and just beneath the surface of the soil. Now here is an important fact to keep in mind. Peonies that are planted too deep will not bloom. In northern gardens plant the tubers no deeper than 2 inches. In my mid-South garden I plant them about a half-inch deep. This allows for the mulch I spread over the planting bed to keep weeds down and help conserve moisture.
Once planted, water well and keep the area consistently moist until the ground freezes.
What to Expect
Next spring your peony will produce foliage, but it may take a few seasons for it to put on a big display of flowers. But your patience will be rewarded. Peonies are plants that are geared for long lives and their blooms improve with age.
The large, heavy flowers of many of the old fashioned varieties such as Sarah Bernhardt and Festiva Maxima have a tendency to flop over. One of the most effective ways to avoid this is to cage them in the early spring soon after the stems emerge from the ground. You can use a simple metal ring with legs on it to give them support or you can just use a piece of wire fencing to encircle the plant.
Another great thing about peonies is their fragrance, but to insure lots of bloom the following year, it's important to remove the seedpods and fertilize each plant in late spring/early summer after deadheading the faded flowers. You can use a blend of 5-10-5 sprinkled around the base. About a handful per plant is enough. This is the only time you need to feed them because too much fertilizer can result in burn, fewer blooms and spindly growth.