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Time To Divide Herbaceous Perennials

One reason perennials are popular is because they flower every year so you don’t have to plant new ones like you do with annuals. Herbaceous perennials are those that die down to the ground each year but whose roots remain alive and send up new top growth each year.

Although herbaceous perennials rebloom every year, they are not completely maintenance-free. One task that’s required every few years is dividing. Perennials like to keep growing. Some spread out and may try to take over the whole planting bed. Others grow new shoots within their original crowns, making them very dense or thick. And still others grow new shoots around the outer edge of the original crown, stressing the original crown.

I recommend dividing perennials after they flower. So, those that flowered in spring and summer should be divided now. Those that are still in bloom shouldn’t be divided until spring. Although the best time to divide is right after they finish blooming, it can be done any time before the ground freezes. The ideal conditions are when the weather is cool, overcast and damp.

It’s best for the plants if you water the ground around them the day before and that you prepare the holes for each section of transplanted perennial before you start removing the parent plant. The holes should be twice as wide as the plant section and just as deep. For best results you should plant all of the sections right after dividing them. If you have to store them, they should be wrapped in moist burlap or covered with mulch.

When digging the parent plant, dig the circle wide enough to keep the root intact. When you get it out of the hole, lay it on a sheet of plastic and remove just enough soil to make the roots visible. If the root system is the spreading type, such as asters, bee balm, Black-eyed Susan, it can often be pulled apart by hand. If you can’t split the roots by hand, use a shovel or garden fork. If the plant has clumping roots, such as Hosta, Lily of the Nile, a sharp shovel, axe or saw will be required to split them. A third type of root, rhizomes, such as Bearded iris, are very fleshy and may be able to be cut with a sharp knife.

To plant the sections, return one to the hole in which you removed the parent plant and plant the others in the new holes you prepared. Backfill, lightly tamping the backfill, water and then mulch.

Dividing does more than prevent your perennials from taking over your planting bed. It also promotes healthy growth, more flowers and makes them more insect and disease resistant. It’s good for perennial growth in the same way that pruning is good for trees and shrubs. As a bonus, divided perennials provide you with free plants for your yard or to share with friends.

If you would rather leave dividing perennials to somebody else, we have just the professionals who are up for the task.

One comment on “Time To Divide Herbaceous Perennials

  1. We will be waiting for autumn before relocating and dividing agapanthus. I trust the weather more than automated irrigation, especially since we may not install the irrigation right away. These are some of the same common blue agapanthus I relocated and divided when I was in junior high school! There are common white agapanthus too that, except for the bloom color, are identical to the blue.

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