Peonies are so hardy they can be grown in hardiness zone 2, the coldest in the United States, and they can also be grown in all of the zones up to the very warm zone 8. Peonies are easy to grow and low maintenance. Peonies come in a wide range of colors, from the pure white to the deepest reds, can be grown in containers and make great cut flowers.
There are just three types of peonies, but within those three types there are at least 35 different varieties. The three types are tree, herbaceous and intersectional. Tree peonies have a wood stem that stays all year long. A tree peony looks like a small shrub with leaves that fall off in autumn. Herbaceous peonies die back to the ground in the fall. Intersectional peonies are a hybrid of both of the other types. They die back to the ground like the herbaceous type, but have flowers and leaves like the tree type.
All peonies form the buds for next year’s leaves and flowers in the fall. The tree peony forms the buds on the above-ground part. This is why tree peonies do not do well in colder climates. The other two types, however, form the buds on the crown, which is below ground and protected from the cold. Some varieties of peonies are slow growers and can take as long as three years to produce flowers.
Peonies love sun and in most places should be planted in full sun. The exception is in areas with the hottest summers, where they can be planted in areas of partial shade. Peonies should not be planted in full shade at any time.
Peonies should be planted with the top eye of the crown no deeper than 2 inches. Peonies do not like to sit in moisture. Make sure the soil is well drained by adding organic compost to the soil. Peonies should be planted in the fall. That is the time when the plant will develop its root system. By the time spring comes, you will have a good strong plant able to stand up to the hottest summers.
Herbaceous and intersectional peonies should be cut back to the ground–just about 2 inches from the ground–in the fall, preferably just after the first hard frost. The leaves will store the food for the winter. Cut them back too early, and the plant will not have the food it needs to winter over.
Peonies are susceptible to fungus infections that can cause the crown to rot, mostly when there is prolonged cold and wet weather. Remove the sick parts of the plant as soon as possible. Fungus can be spread to other plants, so disinfect any tools you use. The fungus will winter over in any leaves that fall off, so in the fall pick everything up and dispose of it.