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Linda Geist
  • Black-eyed Susan “Goldsturm.”
    Black-eyed Susan “Goldsturm.” Photo by F.D. Richards, shared under a Creative Commons (BY) license.
  • Purple coneflower "Magnus."
    Purple coneflower "Magnus," a popular nativar. Photo by Elvert Barnes, shared under a Creative Commons (BY) license.

COLUMBIA, Mo. – As clump-forming perennials mature, they often become overcrowded, competing among themselves for light, water and nutrients. This typically results in fewer blooms, said David Trinklein, state horticulture specialist with University of Missouri Extension.

Don’t despair. “With a little garden surgery, new life can be instilled into ragged, overgrown perennials,” said Trinklein.

While division may seem like a spring task, early fall is ideal, he said. Cooler weather and reduced water stress help plants recover and reestablish roots before winter. Root growth continues into late fall as long as soils remain warm.

Why divide perennials?

Overcrowding stresses plants and reduces flowering. Dividing them restores vigor and lets gardeners expand their beds or share plants with others.

How to divide perennials

  • A sharp spade or garden fork works best.
  • Slice the clump, making sure roots remain intact.
  • Take half the clump with as many roots as possible.
  • Refill the original hole with good soil and replant the removed portion elsewhere, or pass it along to a friend.
  • Keep the soil moist for several weeks while the plant settles in.

What to divide, and what not to

Some perennials thrive when divided, including:

  • Daylilies.
  • Irises.
  • Ornamental grasses.
  • Black-eyed Susans.
  • Purple coneflowers.

Not all perennials require division. Peonies prefer to stay put. If unsure, check plant care recommendations or consult the MU Extension website.

Fertilizing: timing matters

Avoid fertilizing in fall, since winter cold may damage new growth. Wait until spring, when plants break dormancy. Use a balanced fertilizer and follow label instructions.

Share the love

“Gardeners rarely throw away plants,” Trinklein noted. “They use divisions to expand their gardens or share with friends.” Label your divisions so you remember what you planted and where.

Photos

Perennials that thrive when divided include purple coneflower and black-eyed Susan.

Purple coneflower. Photo by Elvert Barnes. Sared under a Creative Commons license (BY-SA 2.0).

Black-eyed Susan. Photo by F.D. Richards. Shared under a Creative Commons license (BY-SA 2.0).

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