There are over 5,000 varieties of the common garden or herbaceous peony. Fall is the opportune time to plant your freshly dug roots. If you purchase a potted root these can be planted anytime of the year. (remember to plant the crown at least 2" below soil and no more than 2" if too low or too high it will hinder flowering)All peonies require a cold period (vernalization)
When planting your herbaceous roots make sure that the bud (little pink nub) is 1 to 2" below soil level. A 3 to 5 eye root will generally flower within 2 years of planting.
Plants will grow between 2 and 4feet tall, in a sunny location (at least 6 hours)in well drained, organic rich soil. Although peonies will tolerate a wide range of soil types. Top dress your peonies each fall with compost to improve soil structure and remember not to place compost directly on crown of plant.
Planting Itersectional Hybrids (cross between a herbaceous and a tree peony) are a little different than herbaceous. Like the herbaceous they like full sun (6 hours or more) and well drained compost rich soil. They can grow up to 4 feet across and live for years with minimal care. Plant your root so the first eye above the crown is at soil level. Eyes may be on the crown or the stem. All visible eyes on crown should be 5 to 10cm under the soil surface and roots always pointing downward. Remember to mulch your Itoh for the first winter and never use fresh manure.
Seasonal Care for Herbaceous and Intersectionals:
Early Spring: If you have insufficient spring rains water. Side dress plants with compost or aged manure. If botrytis blight was present the previous season, cover ground around plant with a thin (one-quarter inch) layer of sand. Set stakes or other supports in place now.
Mid-Spring: Watch for signs of botrytis blight, removing any diseased tissue immediately. Train plants through supports. Remove side buds if exhibition-size blooms are desired.
Late Spring: Deadhead Peonies religiously and remove all fallen petals or blooms from the garden. If you wish to collect seeds leave spent blooms on your plants.
Summer: Herbaceous Peonies do best with an inch of water a week. Check for seeds from your peonies and when ripe (pods open and they turn dark brown or black)remove from seedheads.
Fall: Cut stems of Herbaceous Peonies back to soil level. Dig and divide plants now if necessary. Mulch new plantings with hay or evergreen boughs after the ground freezes.
Few insect pests bother Herbaceous Peonies,
Botrytis a fungal disease more prominent especially in very wet seasons. The stems of your plant develop cankers or blacken at the base and fall over or simply wilt. Leaves may show black or brown patches and buds may turn brown and fail to open. Good culture and sanitation in the garden can help prevent or correct these problems. Plants need good drainage and air circulation, so do not crowd. Remove any affected foliage at the first sign of disease and deadhead religiously, removing all flower parts and petals from the garden. Cut off all foliage just below soil level after a killing frost in the fall and remove it and any debris from the area -- do not compost. If botrytis was present the previous spring, add a shallow layer of sand around the plants and crowns. Fungal spores overwinter at the base of the plants, and spring rains then splash the spores up onto the new shoots. Removing any debris and old foliage and covering the soil with sand helps prevent reinfection.
Phytophthora, another blight may also appear, but the two diseases are hard to tell apart, this disease is usually fatal to the plant and infected plants should be dug up and destroyed, and the soil replaced before replanting.
URBAN MYTH: Ants are often said to be required in order for buds to open. Ants are attracted to sap sacreted by buds and do no harm to the plant.