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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Dividing Hebaceous Perennials

This article was published originally on 4/22/2009

Spring Division of Herbaceous Perennials Herbaceous perennials are commonly divided to control size, retain vigor, encourage more blooms and increase the number of a particular perennial in the landscape. Vigorous perennials may not be model citizens in the planting area and grow so rapidly that they choke out neighboring plants in the flower bed. Other perennials decline in vigor and do not bloom as heavily if not divided. The best time to divide perennials varies with the different plant species. Below is a list of common perennials that should be divided in spring.

  • Aster (Aster species) divide every 2 or 3 years.
  • Astilbe (Astilbe species) divide every 3 or 4 years.
  • Baby's Breath (Gypsophila paniculata) division is difficult.
  • Bee Balm (Monarda didyma) divide approximately every third year.
  • Blanket Flower (Gaillardia x grandiflora) Blazing Star (Liatris species)
  • Chrysanthemum (Dendranthema x grandiflorum) divide every 2 or 3 years.
  • Coral Bells (Heuchera species)
  • Coreopsis (Coreopsis species)
  • Cornflower (Centaurea species) requires frequent division every 2 or 3 years.
  • Daylily (Hemerocallis species)
  • Gooseneck Loosestrife (Lysimachia clethroides) plants spread aggressively. Divide every 2 or 3 years.
  • Hardy Geranium (Geranium species)
  • Hardy Zinnia (Heliopsis helianthoides) divide every other year.
  • Hosta (Hosta species) plants can be left undisturbed for years.
  • Lily-of-the-Valley (Convallaria majalis) plants spread rapidly.
  • Obedient Plant (Physostegia virginiana) plants spread rapidly. Divide plants every 2 or 3 years.
  • Orange Coneflower (Rudbeckia fulgida) divide every 3 or 4 years.
  • Ornamental Grasses
  • Perennial Salvia (Salvia hybrids)
  • Phlox, Garden (Phlox paniculata) divide every 3 to 4 years.
  • Phlox, Moss (Phlox subulata) divide immediately after blooming.
  • Purple Coneflower (Echinacea purpurea) divide every 3 or 4 years.
  • Shasta Daisy (Leucanthemum x superbum) may be short-lived.
  • Speedwell (Veronica species)
  • Spiderwort (Tradescantia virginiana) plants spread rapidly. Divide every 2 or 3 years.
  • Stonecrop (Sedum species)
  • Yarrow (Achillea species) many of the yarrows spread rapidly. Divide every 3 or 4 years.

Year of Publication: 
2009
Issue: 
IC-500( 6) -- April 22, 2009