I have some peonies that never bloom. What can be wrong with them? Several things might prevent them from blooming but the most likely is that they are planted too deeply. Two inches is the proper depth, and beyond that they frequently produce “blind” buds which will not open.
What fertilizer should I use? They will do well with a dressing of bone meal worked in around the plants each spring. A complete balanced fertilizer is also good, and well-rotted manure and leaf mold will help maintain fertility.
How do you take care of tree varieties? Tree peonies need the same soil and in general the same treatment as other varieties. Good drainage, fairly rich soil with a good amount of organic matter, regular cultivation and sun at least half the day, will make them do their best.
When is the best time to transplant them? Late August or early September is the best time of the year to divide and transplant them. That gives the young plants time to get established before winter. If you choose to plant them in the spring, a year’s bloom is usually lost.
Where’s the best spot to plant them? They prefer full sun. Don’t plant under shade trees or on the north side of the home.
How do you divide them? Dig the clumps by digging around the roots on all sides and carefully lifting the clumps. Cut the tops back to about 4″. Don’t break off the side roots. Shake off the excess soil and wash the roots with a hard spray of water. Divide the clumps with a knife or sharp spade. Allow from 3-5 eyes on each clump. Don’t plant the top of the divided clumps more than 2″ deep. They don’t flower when newly planted if the eyes are deeper than 2″. Also, if they are located in a shady area they will flower very sparsely.
I have a white one that blooms but a red one that doesn’t (I live in Mississippi). I have read that they can’t be grown this far south–is this so? The fact that your white one succeeds is proof that they may be grown in your locality. Some varieties are better than others in southern conditions. Felix Crousse and Richard Carvel are two red varieties adapted to the South. Try growing one of them instead of the red you are now having trouble with. They should have enough cold weather to freeze the tops back each winter, and enough water to keep the ground moist, especially at blooming time. Having them in partial shade is an advantage in very hot weather.
One I planted two years ago has not grown much. Its leaves are brown-spotted and it looks as though it may die. What is wrong? It may have the botrytis fungus blight, which is the most serious of peony diseases. This fall scrape the soil away from the crown and cut off all stalks as close to the crown as possible. Burn the old stalks. Next spring when new growth appears, begin spraying with Bordeaux mixture , and keep it up every week or ten days for a couple months.
Source: Vintage WorkBasket Magazine (1954)…Also, the information originally published on Daylilies & Irises: How To Divide & Transplant  was moved here for better organization.