Dividing perennials

Spring-flowers
While many perennials can be divided in either early Spring or early Fall, some are very picky.

Divide by hand

common name

botanical name

Optimal time to divide

Blanket flowers

Gaillardia spp.

Spring / Fall

Bleeding hearts

Dicentra spp.

Spring, after plant flowers

Bugleweed

Ajuga reptans

Spring / Fall

Coral bells

Heuchera spp.

Spring / Fall

Cranesbills

Geranium spp.

Spring / Fall

Creeping Jenny

Lysimachia nummularia

Spring / Fall

Deadnettle

Lamium maculatum

Spring / Fall

Epimediums

Epimedium spp.

Spring, after plant flowers
Fall

Foam flower

Tiarella cordifolia

Spring  / Fall

Forget-me-not

Myosotis sylvatica

Spring, after plant flowers
Fall

Hellebores

Helleborus spp.

Spring, after plant flowers
Fall

Jacob’s ladder

Polemonium caeruleum

Spring / Fall

Lady’s mantle

Alchemilla mollis

Spring / Fall

 Lamb’s ears  Stachys byzantina  Spring / Fall
Moss pink Phlox subulata Fall
Primroses Primula spp. Spring, after plant flowers
Pulmonarias Pulmonaria spp.) Spring, after plant flowers
Fall
Pussytoes Antennaria dioica Spring / Fall
Sea thrift Armeria maritima Spring / Fall
Speedwell Veronica spicata Spring / Fall
Spurge Euphorbia myrsinites Spring, after plant flowers
Fall
Wear protective gloves as sap may irritate skin.
Stonecrop Sedum spectabile Spring / Fall
Sweet woodruff Galium odoratum Fall
Violets, pansies Viola spp. Spring / Fall
Wormwood Artemisia ludoviciana Spring / Fall
Yarrow Achillea millefolium Spring / Fall

Divide with spade or pitchfork

COMMON NAME

BOTANICAL NAME

OPTIMAL TIME TO DIVIDE

African lilies

Agapanthus cvs.

Spring / Fall

Anemone

Anemone × hybrida

Spring

Asters

Aster spp.

Spring

Bee balm

Monarda didyma

Spring / Fall

Bellflowers

Campanula spp.

Spring / Fall

Big bluestem grass

Rudbeckia spp.

Spring / Fall

Black-eyed Susans

Rudbeckia spp.

Spring / Fall

Blood grass

Imperata cylindrica

Spring / Fall

Cardinal flower

Lobelia cardinalis

Spring  / Fall

Catmint

Nepeta × faassenii

Spring  / Fall

Coneflower

Echinacea purpurea

Spring  / Fall

Daisy

Leucanthemum × superbum

Spring / Fall

Daylilies

Hemerocallis spp.

Spring / Fall

Forest grass Hakenochloa macra Spring / Fall
Fountain grass Pennisetum alopecuroides Spring / Fall
Garden phlox Phlox paniculata Spring / Fall
Gaura Gaura lindheimeri Spring / Fall
Goldenrods Solidago spp. Spring / Fall
Gunnera Gunnera manicata Spring / Fall
Speedwell Veronica spicata Spring / Fall
Hostas Hosta spp. Spring / Fall
Japanese painted fern Athyrium niponicum ‘Pictum’ Spring / Fall
Jerusalem sage Phlomis russeliana Spring / Fall
Lemon balm Melissa officinalis Spring / Fall
Ligularia Ligularia dentata Spring / Fall
Masterwort Astrantia major Spring / Fall
Monkshood Aconitum napellus Spring
Penstemons Penstemon spp. Spring / Fall
Perennial sage Salvia × superba Spring, after plant flowers
Fall
Pinks Dianthus plumarius Spring / Fall
Poppies Papaver spp. Fall
Red hot pokers Knifophia spp. Spring / Fall
Sedge Carex morrowii Spring / Fall
Siberian iris Iris sibirica Fall
Silver grasses Miscanthus spp. Spring / Fall
Snakeroot Cimicifuga racemosa Spring / Fall
Switch grass Panicum virgatum Spring / Fall
Tickseed Coreopsis verticillata Spring / Fall
Turtlehead Chelone glabra Spring / Fall
Yarrow Achillea filipendulina Spring / Fall

Slice apart woody crowns with a handsaw

common name

botanical name

Optimal time to divide

Amsonias

Amsonia spp.

Spring / Fall

Astilbes

Astilbe spp.

Spring / Fall

Bear’s breeches

Acanthus spinosus

Spring / Fall

Doll’s eyes

Actaea pachypoda

Spring

Foxtail lilies

Eremurus spp.

Fall

Gayfeather

Liatris spicata

Spring / Fall

Goatsbeard

Aruncus dioicus

Spring / Fall

Joe Pye weed

Eupatorium maculatum

Spring / Fall

Lilyturf

Liriope spicata

Spring  / Fall

Male fern

Dryopteris filix-mas

Spring  / Fall

Meadowsweets

Filipendula spp.

Spring  / Fall

Peonies

Paeonia cvs.

Fall

Solomon’s seal

Polygonatum odoratum

Spring / Fall

Wild indigo Baptisia australis Spring, after flowers bloom

Cut up rhizomes and tubers with a knife

common name

botanical name

Optimal time to divide

Arum

Arum italicum

Fall

Bergenia

Bergenia cordifolia

Spring / Fall

Caladiums

Caladium spp.

Spring

Calla lily

Zantedeschia aethiopica

Spring

Canna lily

Canna spp.

Spring

Corydalis

Corydalis lutea

Spring / Fall

Dahlias

Dahlia cvs.

Spring

Elephant ears

Alocasia spp.

Spring

Irises

Iris spp.

Fall

Lady fern

Athyrium filix-femina

Spring  / Fall

Lily-of-the-valley

Convallaria majalis

Spring  / Fall

Rhubarb

Rheum palmatum

Spring

Rodgersia

Rodgersia pinnata

Spring / Fall

Spurge Euphorbia griffithii Spring / Fall
Wear protective gloves as sap may irritate skin.
Wild ginger Asarum europaeum Spring

These perennials are best not divided

Alyssums, Alyssum spp.
Candytuft, Iberis sempervirens
Carnation, Dianthus caryophyllus
Delphinium, Delphinium × elatum
Euphorbia, Euphorbia characias ssp. wulfenii
Foxgloves, Digitalis spp.
Garden sage, Salvia officinalis
Geraniums, Pelargonium spp.
Lavender cotton, Santolina chamaecyparissus
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

Dividing technique based on roots

Woody roots

woody rootWoody perennials often form roots when stems rest on the ground or are buried by gradually accumulating mulch. Make a new plant by simply cutting between the rooted stem and the mother plant. Plants that have woody roots include candytufts (Iberis spp. and cvs.), euonymus (Euonymus spp. and cvs.), lavenders (Lavandula spp. and cvs.), sages (Salvia spp. and cvs.).

Underground running roots

underground rootUnderground running roots can develop suckers as they grow beyond the shade of the mother clump. These suckers can be cut away from the main plant, or you can dig up the main plant and cut away any piece with an eye or sucker already forming.

Plants with underground running roots include hardy geraniums (Geranium spp.), Japanese anemones (Anemone × hybrida cvs.), ostrich fern (Matteuccia pennsylvanica), plume poppies (Macleaya spp. and cvs.).

Taproots

tap rootPlants that have taproots can be divided by using a sharp knife to slice down the length of the root. Every piece that has at least one eye, some of the taproot, and a few side roots is a viable division.

Plants that have taproots include balloon flowers (Platycodon grandiflorus and cvs.), butterfly weeds (Asclepias tuberosa and cvs.), cushion spurges (Euphorbia polychroma and cvs.), and Oriental poppies (Papaver orientale and cvs.).

Surface roots

surface rootSome perennials have roots that run on or just below the surface of the soil. They form new crowns and roots when they reach open spaces or make contact with the soil. If you cut between any of the stems as you would cut a piece of sod from a lawn, you will have a division with its own stems and roots.

Plants with surface roots include bee balms (Monarda spp. and cvs.), black-eyed susans (Rudbeckia spp. and cvs.), creeping sedums (Sedum spp. and cvs.), and creeping speedwells (Veronica spp. and cvs.).

Offsets

offset rootTo divide a plant whose roots form offsets (small plants growing at the base of a larger one), snap the connection between any of the sections to obtain a piece with ample roots and three or more growing points (or “eyes”). Some denser clumps may have to be cut apart.

Plants that form offsets include asters (Aster spp. and cvs.), coneflowers (Echinacea purpurea and cvs.), hostas (Hosta spp. and cvs.), and tickseeds (Coreopsis spp. and cvs.).