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Timeline Through Landscape Design

A blog to guide home gardeners with seasonal landscape improvements.
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Dividing Peonies

Posted by Nancy Kreith -

If you read my last post I was going to write about cutting and preserving herbs, but since the weather is still cooperating I wish to complete a different landscape task. The landscape improvement I decided to focus on this week is dividing peonies. If you are looking to divide your peonies, this should be done in the next week. September is typically a better time to divide peonies, but time just got away from me this season. Since it is very early in October and the weather is still quite warm, I went ahead and divided my peonies last weekend.

Many times gardeners choose not to divide peonies and that is just fine because they are a long-lived perennial that can last 50 plus years without division. However, sometimes dividing can help to improve the overall landscape. Reasons you many want to divide your peonies include: wanting a greater number of plants (for free), lack of blooms and frequent disease problems.

The main issue with my peony border is that there is inconsistent spacing, lack of full sun in some parts and they were originally planted directly within the lawn without creating a perennial bed just for them. Having the peonies located directly in with the lawn (Photo 1—peony with powdery mildew) is problematic because weedy grass creeps right into the base of the plant and out grows the peony plant.

It is best to provide peonies (and other perennials) with their own garden bed to allow room to grow. It also benefits the plant to mulch around the base in order to hold in moisture and keep weeds to a minimum. With the plants located directly in the lawn, it is difficult to mow around each peony plant. In fact, maintaining that area of the yard has become a dreadful task.

Additionally, the lack of space and sun and competition from the lawn could be reasons why these peonies have been suffering from powdery mildew fungus and lack of blooms. Planting peonies too deep is another reason for lack of flowers. Peonies prefer full sun, but will tolerate part sun.

When dividing peonies follow these steps:

Cut back the foliage (Photo 2).

Dig up about ½ of the plant including numerous buds or "pink eyes" within the root ball.

When dividing the root ball into clumps, make sure each clump includes 3 to 5 pink eyes.

Next take the division with at least 3 eyes and prepare it for replanting by shaking off the soil and cutting off old dry roots (Photo 3).

Prepare the new garden space for the peony divisions by clearing existing vegetation or weeds, loosening the soil and adding 1 inch of organic matter, such as, compost or peat (Photo 4).

Once the new garden space is prepped, place the "pink eyes" pointed side up and plant only 1 to 2 inches deep at 2 to 3 foot spacing between each plant.

One inch of back fill soil can be placed on top of each division and gently pressed down.

So to be clear, that equals 1 inch of organic matter and 1 inch of topsoil to bury the "pink eyes."

Then water in the divided plant.

Special Notes: If the clump does not have at least 3 eyes, it will take longer for the division to bloom (perhaps a 3-year wait time). Adding organic matter to the hole you just dug up around the existing peony and watering it in will benefit the existing "mother" plant. If you use peat or potting mix for organic matter be sure to moisten it before adding it to the base of the plant. If the "pink eyes" are planted too deep (more than 2 inches) then the plant may not flower.

As you can see in Photo 5, I have spaced my peony divisions accordingly. Before winter, I will tackle removing the lawn in between each plant and replace it with mulch to provide a consistent perennial bed. The bed outlined with mulch will be much easier to maintain verse mowing and using a weed-trimmer to manage the lawn in between.

Throughout most of the fall season, continue watering the division at least once per week if it does not rain. In early winter, the plants should be mulched with straw, hardwood chips or pine bark. This will help protect them for the winter. Mulch can be removed next spring if you wish.

As long as you work on this landscape improvement soon, your peonies will be in good shape for next year. If you miss the window of this warm weather, then you should wait until next fall. Fall is the best time to divide peonies.

I will keep you posted as my new peony divisions becomes an actual border.

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