Dividing Perennials

A woman working in her garden and dividing perennials.

Perennial plants are healthiest when they are young and have room to spread. After several seasons of growing perennials they will begin to die out in the center or simply stop flowering. To keep these plants actively growing and healthy, a technique known as 'division' can be performed.

Why divide perennials?

  • The bed is over crowded
  • The center of the plant is dying out
  • The plant is no longer flowering
  • To increase the number of plants

How to divide a perennial:

  • Cut back the foliage and dig the entire plant out of the ground or just simply take out slices of the plant. Look for natural sections to pull apart, or use a knife or saw to cut into pieces. Plant in a new location and be sure to fertilize with Milorganite® and water.
  • Typically, fall is the best time of the year to divide perennials.
  • In cold-winter areas, stop fertilizing perennials by August to encourage them to slow their growth and harden off for winter.
  • In warm-winter areas, fall is a good time to plant perennials. However, in winter check for signs of disease, especially during wet periods, since the plants are growing slowly and conditions are right for rotting to occur.

Below is a list common perennial varieties and the appropriate time to divide these species for the best results. For more information on dividing perennials, download Garden Gate Magazine's chart.

Dividing Perennials Chart
Plant NameTips for Dividing
AsterDivide every 2 or 3 years in spring
AstilbeDivide every 3 or 4 years in spring.
Baby’s BreathDivision is difficult; carefully divide in spring or late summer/early fall.
Basket-of-GoldDivide in late summer/early fall. Basket-of-gold also can be propagated by stem cuttings in spring or late summer.
Bee BalmDivide approximately every third year in spring.
Blanket FlowerDivide in spring.
Blazing StarDivide in spring.
Bleeding HeartBest done in late summer/early fall. Also can be divided in spring.
Butterfly WeedA taproot makes division difficult. However, butterfly weed is easily propagated by seeds.
ChrysanthemumDivide mums every 2 or 3 years in spring.
ColumbineMany species and varieties are short-lived. Division is difficult, carefully divide in late summer.
Coral BellsDivide in spring or late summer/early fall.
CoreopsisDivide in spring or late summer/early fall.
CornflowerRequires division every 2 or 3 years. Divide in spring.
DaylilyDivide in spring or late summer/early fall.
DelphiniumUsually short-lived, division is seldom necessary.
False IndigoDivision is difficult because of its long taproot. Plants can be started from seeds.
Gooseneck LoosestrifePlants spread aggressively. Divide every 2 or 3 years in spring.
Hardy GeraniumDivide in spring or late summer/early fall.
Hardy ZinniaDivide every other year in spring or late summer/early fall.
HostaPlants can be left undisturbed for years. If additional plants are desired, divide clumps in spring or late summer/early fall.
Iris, BeardedDivide every 3 to 4 years in July or August.
Iris, SiberianDivide after blooming in early summer.
Lily-of-the-ValleyA rapidly spreading groundcover, divide in spring.
LungwortDivide in late summer/early fall.
Obedient PlantPlants spread rapidly. Divide plants every 2 or 3 years in spring.
Oriental PoppyDivide when plants die back in mid- to late summer.
Orange ConeflowerDivide every 3 or 4 years in spring.
Ornamental GrassesSpring is the best time to divide ornamental grasses. Also can be divided in late summer/early fall.
PeonyPeonies are long-lived and can be left undisturbed for many years. If additional plants are desired, divide clumps in September.
Perennial SalviaDivide plants in spring.
Phlox, GardenDivide every 3 to 4 years
Phlox, MossDivide plants in spring immediately after blooming.
Purple ConeflowerDivide every 3 to 4 years in spring.
Shasta DaisyDivide in spring.
SpeedwellDivide in spring or late summer / early fall.
YarrowDivide every 2 to 3 years in spring.

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