From the pages of Fine Gardening Magazine

Techniques for Dividing Perennials

The rootballs of some perennials can be simply pulled apart with your hands; others need to be sliced with a spade or even cut with a saw. Here’s a list of dozens of perennials and the best way to divide them.

by Todd Meier

When dividing perennials, timing and technique are important. And while many perennials can be divided in either early spring or early fall, some are very picky. The optimal time to divide specific perennials is denoted by (S) for spring and (F) for early fall. A single asterisk indicates that division should take place after the plant flowers. Two asterisks mean that protective gloves should be worn when dividing the plant, since its sap may irritate skin.

Divide these plants by hand

• Blanket flowers (Gaillardia spp.) S/F
  
• Bleeding hearts (Dicentra spp.) S*
  
• Bugleweed (Ajuga reptans) S/F
  
• Columbines (Aquilegia spp.) S/F
  
• Coral bells (Heuchera spp.) S/F
  
• Cranesbills (Geranium spp.) S/F
  
• Creeping Jenny (Lysimachia nummularia) S/F
  
• Deadnettle (Lamium maculatum) S/F
  
• Epimediums (Epimedium spp.) S*/F
  
• Foam flower (Tiarella cordifolia) S/F
  
• Forget-me-not (Myosotis sylvatica) S*/F
  
• Hellebores (Helleborus spp.) S*/F
  
• Jacob's ladder (Polemonium caeruleum) S/F
  
• Lady's mantle (Alchemilla mollis) S/F
  
• Lamb's ears (Stachys byzantina) S/F
  
• Moss pink (Phlox subulata) F
  
• Primroses (Primula spp.) S*
  
• Pulmonarias (Pulmonaria spp.) S*/F
  
• Pussytoes (Antennaria dioica) S/F
  
• Sea thrift (Armeria maritima) S/F
  
• Speedwell (Veronica spicata) S/F
  
• Spurge (Euphorbia myrsinites) S/F**
  
• Stonecrop (Sedum spectabile) S/F
  
• Sweet woodruff (Galium odoratum) F
  
• Violets, pansies (Viola spp.) S/F
  
• Wormwood (Artemisia ludoviciana) S/F
  
• Yarrow (Achillea millefolium) S/F

Divide these plants with a spade or pitchfork

• African lilies (Agapanthus cvs.) S/F
  
• Anemone (Anemone X hybrida) S
  
• Asters (Aster spp.) S
  
• Bee balm (Monarda didyma) S/F
  
• Bellflowers (Campanula spp.) S/F
  
• Big bluestem grass (Andropogon gerardii) S/F
  
• Black-eyed Susans (Rudbeckia spp.) S/F
  
• Blood grass (Imperata cylindrica) S/F
  
• Cardinal flower (Lobelia cardinalis) S/F
  
• Catmint (Nepeta X faassenii) S/F
  
• Coneflower (Echinacea purpurea) S/F
  
• Daisy (Leucanthemum X superbum) S/F
  
• Daylilies (Hemerocallis spp.) S/F
  
• Forest grass (Hakenochloa macra) S/F
  
• Fountain grass (Pennisetum alopecuroides) S/F
  
• Garden phlox (Phlox paniculata) S/F
  
• Gaura (Gaura lindheimeri) S/F
  
• Goldenrods (Solidago spp.) S/F
  
• Gunnera (Gunnera manicata) S/F
  
• Hostas (Hosta spp.) S/F
  
• Japanese painted fern (Athyrium niponicum 'Pictum') S/F
  
• Jerusalem sage (Phlomis russeliana) S/F
  
• Lemon balm (Melissa officinalis)
  
• Ligularia (Ligularia dentata) S/F
  
• Masterwort (Astrantia major) S/F
  
• Monkshood (Aconitum napellus) S
  
• Penstemons (Penstemon spp.) S/F
  
• Perennial sage (Salvia X superba) S*/F
  
• Pinks (Dianthus plumarius) S/F
  
• Poppies (Papaver spp.) F
  
• Red hot pokers (Knifophia spp.) S/F
  
• Sedge (Carex morrowii) S/F
  
• Siberian iris (Iris sibirica) F
  
• Silver grasses (Miscanthus spp.) S/F
  
• Snakeroot (Cimicifuga racemosa) S/F
  
• Switch grass (Panicum virgatum) S/F
  
• Tickseed (Coreopsis verticillata) S/F
  
• Turtlehead (Chelone glabra) S/F
  
• Yarrow (Achillea filipendulina) S/F
  

Slice apart woody crowns with a handsaw

• Amsonias (Amsonia spp.) S/F
  
• Astilbes (Astilbe spp.) S/F
  
• Bear's breeches (Acanthus spinosus) S/F
  
• Doll's eyes (Actaea pachypoda) S
  
• Foxtail lilies (Eremurus spp.) F
  
• Gayfeather (Liatris spicata) S/F
  
• Goatsbeard (Aruncus dioicus) S/F
  
• Joe Pye weed (Eupatorium maculatum) S/F
  
• Lilyturf (Liriope spicata) S/F
  
• Male fern (Dryopteris filix-mas) S/F
  
• Meadowsweets (Filipendula spp.) S/F
  
• Peonies (Paeonia cvs.) F
  
• Solomon's seal (Polygonatum odoratum) S/F
  
• Wild indigo (Baptisia australis) S*/F
  

Cut up rhizomes and tubers with a knife

• Arum (Arum italicum) F
  
• Bergenia (Bergenia cordifolia) S/F
  
• Caladiums (Caladium spp.) S
  
• Calla lily (Zantedeschia aethiopica) S
  
• Cannas (Canna spp.) S
  
• Corydalis (Corydalis lutea) S/F
  
• Dahlias (Dahlia cvs.) S
  
• Elephant ears (Alocasia spp.) S
  
• Irises (Iris spp.) F
  
• Lady fern (Athyrium filix-femina) S/F
  
• Lily-of-the-valley (Convallaria majalis) S/F
  
• Rhubarb (Rheum palmatum) S
  
• Rodgersia (Rodgersia pinnata) S/F
  
• Spurge (Euphorbia griffithii) S/F**
  
• Wild ginger (Asarum europaeum) S
  

These perennials are best not divided

• Alyssums (Alyssum spp.)
  
• Candytuft (Iberis sempervirens)
  
• Carnation (Dianthus caryophyllus)
  
• Delphinium (Delphinium X elatum)
  
• Euphorbia (Euphorbia characias ssp. wulfenii)
  
• Foxgloves (Digitalis spp.)
  
• Garden sage (Salvia officinalis)
  
• Geraniums (Pelargonium spp.)
  
• Lavender cotton (Santolina chamaecy-parissus)
  
• Lavenders (Lavandula spp.)
  
• Rose campion (Lychnis coronaria)
  
• Rosemary (Rosmarinus officinalis)
  
• Russian sage (Perovskia atriplicifolia)
  
• Sea hollies (Eryngium spp.)
  
• Silvermound (Artemisia schmidtiana)
  
• Sweet pea (Lathyrus latifolius)
  
• Trillium (Trillium grandiflorum)
  

Todd Meier, Fine Gardening's executive editor, learned to divide perennials as a student at the New York Botanical Garden. For more information on this subject, see Dividing Perennials: Tools, Techniques, and Timing.

From Fine Gardening #72, p. 79 Purchase back issues