Good ol' die-to-the-ground, pop-up-next-spring-bigger-and-better peonies are popular for a lot of reasons. Good foliage. Beautiful flowers with a wide range of colors, forms and fragrance. Great as cut flowers. Rock hardy. Low maintenance. Many even show lovely fall color.
Aside from generous sun and well-drained soil the only thing peonies ask is to be left undisturbed. A Hosta can be moved around like a sofa, and at practically any time of year as long as a few precautions are taken. Peonies, on the other hand, are homebodies and like to settle in one place for years, even decades.
So, what's the difference between planting, transplanting and dividing a peony? You can plant a potted peony any time you can work the soil - April through November. Why? Because you're not disturbing the root system. You're just giving the roots more elbow room to grown when you remove it from the pot.
Transplanting and dividing are more stressful :( and time-sensitive. Transplanting is moving an established peony plant (say, 2 or more years in the ground). Peonies don't mind that if it is done at the proper time, which is mid-August through early November. Even so, moving at that right time is still an adjustment. The plant will take a minimum of a year to get its roots back and start performing normally.
|Peony ready for "washing"|
|Peony root with red "eyes" showing|
In the fall you can cut off current year's stems to work around the plant, and see the roots and eyes better. When digging up to transplant or divide make sure you use a sharp spade. A well-established peony (15 or more stems) can have a root system like a large shrub. Dig deeply and life the entire root system intact. I like to place them on a paved surface and turn the hose on the (car wash nozzle stream). The point is to wash the soil away to check for number and health of eyes and roots.
|Cleaned root, ready for dividing|
At this point cut any damaged, soft or obviously diseased portions off. If you're transplanting think twice about putting a big multi-stemmed (again 15 or more stems) plant back in the ground intact. There's something less vigorous about a mature, woody plant and how quickly it will rebound. Consider dividing it down to 7-10 eyes. In my experience this is best accomplished with a big, sharp kitchen knife. Look for natural separations where you can cut through creating multiple plants with strong roots.
Another word of caution - Don't go to extremes and cut down to 1-3 eye divisions. Those would take several years to get the stem count up so you have a blooming plant. A nursery standard is called a 3-5 eye division. That will give you a nice sized, vigorous plant that MAY produce a bloom or two the spring after transplanting.
|Peony divisions ready for planting|
A you prepare the hole be sure to thoroughly mix 1 part organic matter (well-aged compost or dehydrated manure, NEVER fresh) to 3 parts soil taken from the planting hole. The only other caution is to make sure you don't plant too deeply. If the uppermost eyes are placed or settle more than 2" below the finished soil grade you'll never have flowers. Leaves yes, but probably no flowers.
As you now know, the answer to the question of fall peony is: planting, transplanting and dividing = yes. Enjoy for a lifetime.