Dividing Perennials

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Dividing Perennials

• Mike Maddox
• Rock County UW-Extension

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Plant Propagation

• Sexual Propagation
• Exchange of genetic materials
• Asexual (Vegetative) Propagation
• Cloning of an individual

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Life Cycles

• Perennial
• Lives more than two years
• Herbaceous perennials
• Woody perennials

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Dividing Perennials

• Control size
• Rejuvenation
• Increase numbers

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When to Divide

• Reduced plant size
• Reduced flowering
• Dead areas
• Sparse bottom foliage
• Depends on the species

Spring blooming plants divide in the fall fall
blooming plants divide in the spring.
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Preparation

• Before dividing
• Water plants thoroughly
• Prune stems and foliage

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Lifting

• Use sharp shovel or spading fork
• Cut in on all sides of plant
• 4 to 6 inches from crown
• Pry under plant

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Separation

• Remove loose soil
• Remove dead leaves and stems
• Note root system of plant
• Spreading
• Clumping
• Rhizome
• Tuber

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Separation

• Spreading root systems
• Many slender roots from center of plant
• Plants can be invasive
• Cut with shears or pulled apart by hand
• Asters, bee balm, lambs ear, purple coneflower,
  many common perennials

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Separation

• Clumping root systems
• Many fleshy roots from crown of plant
• Can crowd own centers
• Keep one bud/eye with each division
• Astilbes, hostas, daylilies, orn. Grasses

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Separation

• Rhizome division
• Horizontal stems, Primarily bearded iris
• Divide after flowering through fall
• Cut and discard rhizome sections gt 1 year
• Inspect for disease and insect damage
• Cut back leaves to fans
• Replant with top of rhizome above soil level

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Separation

• Tuberous roots
• Enlarged roots for storage
• Divide with sharp knife
• Each root must contain stem tissue and bud
• Can be replanted or stored
• Dahlias

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Plants better left alone

• Dont divide
• (Asclepias) euphorbias, oriental poppies, babys
  breath (Gypsophila), gas plant (Dictamnus albus),
  Japanese anemones, false indigo (Baptisia) and
  columbines (Aquilegia), Lenten and Christmas
  roses (Helleborus), more

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Common Perennials to Divide
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• Asters (Aster)
• Every year or two to control spread and maintain
  vigor. Spring
• Spreading root division. Replant outer growth and
  discard the centers of older plants.

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• Astilbe (Astilbe)
• Every 2 to 3 years as plants become crowded.
  Early Spring or fall.
• Clumping root division. Needs division for best
  bloom.

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• Bearded Iris (Iris)
• Every 3 to 4 years. After flowering up to
  September.
• Rhizome root division.

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• Bee balm (Monarda)
• Every 3 years to control rampant growth. Spring
  or fall.
• Spreading root division.

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• Bellflower (Campanula)
• Every 2 to 3 years or as the plant becomes
  crowded. Spring or early fall.
• Spreading root division.

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• Blackberry Lily (Belamcanda)
• Every 3 to 4 years after bloom is finished.
• Rhizomes should be treated as iris.

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• Black-eyed Susan (Rudbeckia fulgida)
• Every 3 to 4 years. Early spring or fall.
• Spreading root division.

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• Blanket Flower (Gaillardia grandiflora)
• Every 1 or 2 years to maintain vigor. Early
  spring.
• Spreading root division.

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• Bleeding Heart (Dicentra)
• Rarely needs division. Early spring.
• Fleshy root division. Be gentle with brittle
  roots.

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• Cannas (Canna)
• Every 3 or 4 years, or as desired to increase
  stock. Spring.
• Fleshy root system, rhizome

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• Chrysanthemum (Chrysanthemum)
• Every year or two. Spring.
• Spreading root division.

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• Cranesbill (Geranium)
• Every 2 to 4 years. Spring or fall.
• Spreading root division.

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• Daylily (Hemerocallis)
• Every 3 to 6 years or as desired to increase
  stock. Spring, summer or fall. Ideal time is
  after bloom is finished.
• Divide fleshy roots into segments with roots.
  Divisions with three or more shoots will bloom
  sooner.

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• Garden Peony (Paeonia)
• For plant increase, rarely needs division.
  Divisions may wait up to 3 years before blooming.
  September or October.
• Divisions should have three to five
  well-developed eyes (buds for next years
  growth). Plant peonies with the eyes no deeper
  than 1 inch below the surface.

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• Garden Phlox (Phlox paniculata)
• Every 3 to 4 years. Early spring or fall.
• Spreading root division.

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• Hosta (Hosta )
• Rarely need division and will reach their best
  form if not divided too often. They can be
  divided as needed for plant increase. Early
  spring or early fall.
• Fleshy root division. Divide into clumps with one
  to three eyes. A wedge can be taken from an
  established plant, which will soon fill back in.

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• Lambs-ear (Stachys byzantina)
• Every 2 to 3 years. Spring or early fall.
• Spreading divisions. Discard weak centers.

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• Lily of the Nile (Agapanthus)
• When flowering slows due to crowding. Spring,
  summer or fall
• Fleshy clumping roots are large and brittle. Do
  not divide unless needed to improve bloom.

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• Lily of the Valley (Convallaria majalis)
• Divide for plant increase as desired. Early
  spring.
• Can be divided as clumps or single "pips".

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• Ornamental Grasses
• Every 3 to 4 years. Spring for most grasses. Many
  grasses do not tolerate fall division.
• Very dense fibrous root system may require the
  use of an ax or saw to divide.

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• Purple cone-flower (Echinacea)
• Every 4 years. Spring or fall.
• Spreading root division.

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• Red-hot-poker (Kniphofia)
• Divide only for plant increase. Spring or fall.
• Fleshy clumping root system. Divisions may take
  2-3 years to bloom.

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• Tall sedum (Sedum)
• For plant increase. Spring.
• Clump divisions.

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• Tickseed (Coreopsis)
• Every 1 or 2 years to maintain vigor. Spring or
  fall.
• Spreading root division. Discard weak center.

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• Wormwoods (Artemisia)
• Every year or two for spreading wormwoods like
  Silver King and Valerie Finnis. Spring.
• Spreading root division, or remove excess and
  dead center. Do not divide woody artemesias.

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• Yarrow (Achillea)
• Every 2 or 3 years or when center dies out.
  Spring or fall.
• Spreading root division.

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