Different Perennial Plant Root Systems

Different Perennial Plant Root Systems

Offsets

To 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 (Asterspp. and cvs., USDA Hardiness Zones 4–8), coneflowers (Echinacea purpureaand cvs., Zones 3–9), hostas (Hostaspp. and cvs., Zones 3–8), tickseeds (Coreopsisspp. and cvs., Zones 4–9).

Surface roots

Some 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 (Monardaspp. and cvs., Zones 4–9), black-eyed Susans (Rudbeckiaspp. and cvs., Zones 3–9), creeping sedums (Sedumspp. and cvs., Zones 3–9), and creeping speedwells (Veronicaspp. and cvs., Zones 3–8).

Taproots

Plants 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 grandiflorusand cvs., Zones 4–9), butterfly weeds (Asclepias tuberosaand cvs., Zones 4–9), cushion spurges (Euphorbia polychromaand cvs., Zones 4–9), and Oriental poppies (Papaver orientaleand cvs., Zones 4–9).

Underground running roots

Underground 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 (Geraniumspp. and cvs., Zones 4–9), Japanese anemones (Anemone × hybridacvs., Zones 4–8), ostrich fern (Matteuccia pennsylvanica, Zones 3–8), and plume poppies (Macleayaspp. and cvs., Zones 4–9).

Woody roots

Woody 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 (Iberisspp. and cvs., Zones 5–9), euonymus (Euonymusspp. and cvs., Zones 4–9), lavenders (Lavandulaspp. and cvs., Zones 5–10), and sages (Salviaspp. and cvs., Zones 5–10).

Timing is important

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 (Gaillardiaspp.) S/F
Bleeding hearts (Dicentraspp.) S*
Bugleweed (Ajuga reptans) S/F
Columbines (Aquilegiaspp.) S/F
Coral bells (Heucheraspp.) S/F
Cranesbills (Geraniumspp.) S/F
Creeping Jenny (Lysimachia nummularia) S/F
Deadnettle (Lamium maculatum) S/F
Epimediums (Epimediumspp.) S*/F
Foam flower (Tiarella cordifolia) S/F
Forget-me-not (Myosotis sylvatica) S*/F
Hellebores (Helleborusspp.) 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 (Primulaspp.) S*
Pulmonarias (Pulmonariaspp.) 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 (Violaspp.) S/F
Wormwood (Artemisia ludoviciana) S/F
Yarrow (Achillea millefolium) S/F

Divide these plants with a spade or pitchfork
African lilies (Agapanthuscvs.) S/F
Anemone (Anemone × hybrida) S
Asters (Asterspp.) S
Bee balm (Monarda didyma) S/F
Bellflowers (Campanulaspp.) S/F
Big bluestem grass (Andropogon gerardii) S/F
Black-eyed Susans (Rudbeckiaspp.) S/F
Blood grass (Imperata cylindrica) S/F
Cardinal flower (Lobelia cardinalis) S/F
Catmint (Nepeta × faassenii) S/F
Coneflower (Echinacea purpurea) S/F
Daisy (Leucanthemum × superbum) S/F
Daylilies (Hemerocallisspp.) 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 (Solidagospp.) S/F
Gunnera (Gunnera manicata) S/F
Hostas (Hostaspp.) 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 (Penstemonspp.) S/F
Perennial sage (Salvia × superba) S*/F
Pinks (Dianthus plumarius) S/F
Poppies (Papaverspp.) F
Red hot pokers (Knifophiaspp.) S/F
Sedge (Carex morrowii) S/F
Siberian iris (Iris sibirica) F
Silver grasses (Miscanthusspp.) 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 (Amsoniaspp.) S/F
Astilbes (Astilbespp.) S/F
Bear’s breeches (Acanthus spinosus) S/F
Doll’s eyes (Actaea pachypoda) S
Foxtail lilies (Eremurusspp.) 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 (Filipendulaspp.) S/F
Peonies (Paeoniacvs.) 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 (Caladiumspp.) S
Calla lily (Zantedeschia aethiopica) S
Cannas (Cannaspp.) S
Corydalis (Corydalis lutea) S/F
Dahlias (Dahliacvs.) S
Elephant ears (Alocasiaspp.) S
Irises (Irisspp.) 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 (Alyssumspp.)
Candytuft (Iberis sempervirens)
Carnation (Dianthus caryophyllus)
Delphinium (Delphinium × elatum)
Euphorbia (Euphorbia characiasssp. wulfenii)
Foxgloves (Digitalisspp.)
Garden sage (Salvia officinalis)
Geraniums (Pelargoniumspp.)
Lavender cotton (Santolina chamaecyparissus)
Lavenders (Lavandulaspp.)
Rose campion (Lychnis coronaria)
Rosemary (Rosmarinus officinalis)
Russian sage (Perovskia atriplicifolia)
Sea hollies (Eryngiumspp.)
Silvermound (Artemisia schmidtiana)
Sweet pea (Lathyrus latifolius)
Trillium (Trillium grandiflorum)