Botanical
Name
Common
Name
|
How
Often To Divide
Season
To Divide
|
Method
Of Division
|
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. |
Astilbe
(Astilbe)
|
Every
2 to 3 years as plants become crowded.
Early Spring or fall.
|
Spreading
root division. Needs division for best bloom. |
Bearded
Iris
(Iris)
|
Every
3 to 4 years.
After flowering up to September.
|
Rhizome
root division. |
Beebalm
(Monarda)
|
Every
3 years to control rampant growth.
Spring or fall.
|
Spreading
root division. |
Bellflower
(Campanula)
|
Every
2 to 3 years or as the plant becomes crowded.
Spring or early
fall.
|
Spreading
root division. |
Blackberry
Lily
(Belamcanda)
|
Every
3 to 4 years
After bloom is finished.
|
Rhizomes
should be treated as iris. |
Black-eyed
Susan
(Rudbeckia
fulgida)
|
Every
3 to 4 years.
Early spring or fall.
|
Spreading
root division. |
Blanket
Flower
(Gaillardia
grandiflora)
|
Every
1 or 2 years to maintain vigor.
Early spring.
|
Spreading
root division. |
Bleeding
Heart
(Dicentra)
|
Rarely
needs division.
Early spring.
|
Fleshy
root division. Be gentle with brittle roots. |
Cannas
(Canna)
|
Every
3 or 4 years, or as desired to increase stock.
Spring.
|
Fleshy
root system. |
Chrysanthemum
(Chrysanthemum)
|
Every
year or two.
Spring.
|
Spreading
root division. |
Cranesbill
(Geranium)
|
Every
2 to 4 years.
Spring or fall.
|
Spreading
root division. |
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. |
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
year’s growth). Plant peonies with the eyes no deeper than 1
inch below the surface. |
Garden
Phlox
(Phlox
paniculata)
|
Every
3 to 4 years.
Early spring or fall.
|
Spreading
root division. |
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. |
Lambs-ear
(Stachys
byzantina)
|
Every
2 to 3 years.
Spring or early fall.
|
Spreading
divisions. Discard weak centers. |
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. |
Lily
of the Valley
(Convallaria
majalis)
|
Divide
for plant increase as desired.
Early spring.
|
Can
be divided as clumps or single "pips". |
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. |
Purple
cone-flower
(Echinacea)
|
Every
4 years.
Spring or fall.
|
Spreading
root division. |
Red-hot-poker
(Kniphofia)
|
Divide
only for plant increase.
Spring or
fall.
|
Fleshy
clumping root system. Divisions may take 2-3 years to bloom. |
Tall
sedum
(Sedum '
Autumn Joy')
|
For
plant increase.
Spring.
|
Clump
divisions. |
Tickseed
(Coreopsis)
|
Every
1 or 2 years to maintain vigor.
Spring or fall.
|
Spreading
root division. Discard weak center. |
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. |
Yarrow
(Achillea)
|
Every
2 or 3 years or when center dies out.
Spring or fall.
|
Spreading
root division. |