I like to move and/or divide most perennial plants in early spring, as close to when they emerge from the ground as possible, as I find I get the highest success rate. Fall is the second best time to plant or divide most perennials. But peonies are different—they are best divided or moved in the fall. This is when you will have the most success with them.
That’s my #1 tip, when people ask me about moving peonies. My #2 tip, is to make sure you don’t plant them too deeply, as if you do, they won’t bloom.
How deep is too deep? Before you move them from their original spot, or, if you’ve just purchased them and they’re still in the pot, take a good look at how high the soil comes on the plants now–you’ll see that it just covers the roots. When you transplant them, you will want to place them in the ground exactly that deep.
And the third tip to successfully moving peonies—plant them in a location that gets six or more hours of direct sun every day. I just moved one that had been in a sunny location, but the sun disappeared as my magnolia tree grew. The last few years it had fewer and fewer blooms, and this year there were none. As of this afternoon, it’s now in a much sunnier spot, and I expect it will be much happier.
Moving a peony isn’t any different from digging up and moving most any other plant, except it might be a bit bigger than you’re used to. Prepare the hole where it’s going before you dig it up from its current location. Dig up the plants and as much of the root as possible and support the roots as you move it to its new location (i.e. do not grab it by the stem and let the roots hang—it would be good to keep as much of the original soil packed around the roots as possible). Pop it into the hole you’ve prepared, paying attention to how deeply you place it (see above), backfill the hole with soil, and water it well (to the point of making mud, for this first watering, is good). Step around the edge of the plant to dislodge any air bubbles and ensure that the roots all have contact with the earth. Especially in colder climates, covering the ground with a layer of mulch is a good idea—it’s an extra layer of insulation to help keep the plant from heaving out of the ground with frost that first winter, when it’s not yet well anchored.
Note: the following does not apply to tree peonies. They’re a woody shrub and are sometimes grafted onto herbaceous peony rootstock. I do not believe they can be divided–you would need to propagate them from cuttings or by other means.
If your herbaceous or Itoh peonies are really big and you want to divide them, do that once you’ve dug the whole plant up. Take a big sharp knife (a Hori Hori knife*, or I’ve even used a saw) and slice the root ball vertically. Make sure there’s still a substantial chunk of root with each section you plant (i.e. don’t try and get 15 plants out of one). Then plant each section individually.
Moving peonies in spring
Spring is not the best time to move herbaceous peonies, fall is. However, sometimes, like when we’re moving houses or impending construction threatens our garden, we have no choice—it’s a case of move it or lose it!
Peonies are generally very hardy plants but they will be stressed by a move in spring. I know it’s painful to do, but if you move peonies in spring, you would be doing them a favour if you cut off any flower buds as they emerge. This will let the plant focus its energy on root development, instead of on reproduction (flowers and seeds), the first year. Be extra vigilant that first summer in keeping it appropriately watered and it should be well settled and back to floriferous splendour in its second year.
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