When to Divide Perennials

Perennials can often be divided to control size, retain vigor and to share with a friend. Other perennials decline if not divided every few years at the appropriate time. One of the easiest ways to propagate your prized perennials is to divide the plant into two or more. To divide a perennial, either cut down into the clump with a sharp spade and lift out the separate chunks, or dig up the entire plant and pry it apart by hand.
 

• Aster - Divide every 2-3 years in spring

• Astilbe - Divide every 3-4 years in spring

• Baby’s Breath (Gypsophila) - Division is difficult, carefully divide in spring or late summer/early fall

• Basket-of-Gold (Aurinia) - Divide in late summer/early fall. 

• Bee Balm (Monarda) - Divide approx. every third year in spring

• Blanket Flower (Gaillardia) - Divide in spring

• Blazing Star (Liatris) - Divide in spring

• Bleeding Heart (Dicentra) - Division is difficult, best done in late summer/early fall

• Butterfly Weed (Asclepias) - A taproot makes division difficult.  Easily propagated by seeds

• Chrysanthemum - Divide every 2-3 years in spring

• Columbine (Aquilegia) - Many species and varieties are short lived. Division is difficult,
  carefully divide in late summer

• Coral Bells (Heuchera) - Divide in spring or late summer/early fall

• Coreopsis - Divide in spring or late summer/early fall

• Cornflower (Centaurea) - Requires division every 2-3 years.  Divide in spring

• Daylily (Hemerocallis) - Divide in spring or late summer/early fall

• Delphinium - Usually short-lived , division is seldom necessary

• False Indigo (Baptisia) - Division is difficult because of its long taproot.  Plants can be started from seeds

• Gooseneck Loosestrife (Lysimachia clethroides) - Plants spread aggressively.  Divide every 2-3 years in spring

• Hardy Geranium (Geranium) - Divide in spring or late summer/early fall

• Ox Eye (Heliopsis) - Divide every other year in spring or late summer/early fall

• Hosta - Plants can be left undisturbed for years.  If additional plants are desired, divide clumps in spring or late summer/early fall

• Iris, Bearded (Iris germanica) - Divide every 3-4 years in July or August

• Iris, Siberian (Iris sibirica) - Divide after blooming in early summer

• Lily of the Valley (Convallaria) - A rapidly spreading groundcover, divide in spring

• Lungwort (Pulmonaria) - Divide in late summer/early fall

• Obedient Plant (Physostegia) - Plants spread rapidly.  Divide plants every 2-3 years in spring

• Oriental Poppy (Papaver) - Divide when plants die back in mid to late summer

• Ornamental Grass - The best time is spring. Also can be divided in late summer/early fall

• Peony - Peonies are long-lived and can be left undisturbed for years.  If additional plants are
  desired, divide clumps in September

• Perennial Salvia (Salvia) - Divide plants in spring

• Phlox, Garden (Phlox paniculata) - Divide every 3-4 years in spring or late summer/early fall

• Phlox, Moss (Phlox subulata) - Divide plants in spring immediately after blooming

• Purple Coneflower (Echinacea) - Divide every 3-4 years in spring

• Shasta Daisy (Leucanthemum) - Tends to be short-lived.  Divide plants in spring

• Speedwell (Veronica) - Divide in spring or late summer/early fall

• Spiderwort (Tradescantia) - Divide every 2-3 years in spring

• Stonecrop (Sedum) - Divide in spring

• Yarrow (Achillea) - Many of the Yarrows spread rapidly.  Divide every 3-4 years in spring