Dividing Perennials
Scientific name | Name | How often to divide | When to divide | |
Achillea spp. | Yarrow | 1 to 3 years | Spring | Separate by cutting or pulling apart. Discard central woody core. |
Acontium napellus | Monkshood | 10+ years | Spring | Resents disturbance. Due to poisonous nature of roots, use rubber gloves when dividing tuberous roots. |
Adiantum pedatum | Maidenhair Fern | Spring | ||
Aegopodium podagraria 'Variegatum' | Snow-on-the-Mountain | 1 to 3 years | Spring or Fall | |
Ajuga reptans | Bugleweed | 1 to 3 years | Spring or Fall | Can be divided any time of year, but spring and fall are best for quick rooting. |
Alchemilla mollis | Lady's Mantle | 6 to 10 years | Spring (or Early Fall) | Cut crown into sections with sharp spade or knife. |
Allium spp. | Ornamental Onion | Fall | Divide overcrowded clusters after foliage disappears. Plant "new" bulbs in fall. | |
Anemone spp. | Anemone | 10+ years | Spring | Resents disturbance. |
Aquilegia spp. | Columbine | 10+ years | Spring (or Late Summer) | Does not like to be disturbed. Dig deep to get all tapering, finger-like roots. Cut youngplant apart with a sharp knife. |
Arisaema triphylla | Jack-in-the-Pulpit | Fall | Divide offsets when plant is dormant | |
Armeria spp. | Thrift | 4 to 5 years | Spring | |
Artemisia spp. | Artemisia | 4 to 5 years | Spring | Regular division is important for health of plant and helps keep its invasive nature under control. Discard weak central crown. |
Aruncus dioicus | Goats Beard | 10+ years | Spring or Fall | Deep rootstock resents disturbance. Use knife to cut woody crown. |
Asarum spp. | Ginger | 6 to 10 years | Spring or Early Fall | Use sharp knife to cut rhizome. |
Asclepias spp. | Milkweed | 10+ years | Does not like to be disturbed. Dig deep to avoid damaging deep taproots. Cut crown apart with sharp knife. Rootstocks are brittle. | |
Aster spp. | Aster | 1 to 3 years | Spring or Fall | Many cultivars require frequent division and replanting of small, healthy pieces from the outside of the clump. |
Astilbe x arendsii | Astilbe | 1 to 3 years | Spring (or Fall) | Needs division for best bloom. Cut plant into sections with sharp spade or knife. |
Astrantia spp. | Masterwort | 4 to 5 years | Spring or Fall | Divide with spade or pitchfork. |
Athyrium filix-femina | Lady Fern | Spring or Fall | Use sharp knife to cut rootstock. | |
Athyrium niponicum | Japanese Painted Fern | Spring or Fall | Use sharp knife to cut rootstock. | |
Aubrieta deltoidea | Rockcress | Spring | ||
Aurinia saxatilis | Basket of Gold | Spring | Difficult because plants clump | |
Baptisia australis | False Blue Indigo | 10+ years | Spring | Resents disturbance. Dig deep to remove entire root system without breaking it. Cut crown apart with sharp knife or saw. |
Bergenia cordifolia | Heart Leaf Bergenia | 4 to 5 years | Spring or Summer | Cut rhizome with sharp knife. Transplant divisions fairly deep into soil. |
Boltonia asteroides | Boltonia | 4 to 5 years | Spring or Early Fall | |
Brunnera macrophylla | False Forget-me-not | 6 to 10 years | Spring or Fall (Late Summer) | |
Caltha palustris | Marsh Marigold | After flowering - May or June | ||
Campanula spp. | Bellflower | 4 to 5 years | Spring or Late Summer (August) | Cut thick, fleshy rootstock apart with sharp knife. |
Carex spp. | Sedge | Spring | Divide with spade or pitchfork. | |
Catanache caerulea | Cupid's Dart | 1 to 3 years | Fall or Spring | |
Centaurea montana | Cornflower | 1 to 3 years | Spring (or Fall) | |
Cerastium tomentosum | Snow-in-summer | 1 to 3 years | Spring or Fall | Can be divided virtually anytime. |
Chelone spp. | Turtlehead | 4 to 5 years | Spring | When young offshoots are 1" high, dig with spade to sever from parent plant. |
Cimicifuga racemosa | Snakeroot or Bugbane | 10+ years | Spring | Resents disturbance. Cut plant into sections with sharp knife or spade. Discard old, woody, central clump. |
Clematis spp. | Clematis | 10+ years | Spring | Divisions on only selected species. Cut crown apart with sharp knife or spade. |
Convallaria majalis | Lily of the Valley | Spring or After Flowering | Divide to keep invasive nature under control. | |
Coreopsis | Tickseed | 1 to 3 years | Spring (or Early Fall) | Cut crown apart with sharp knife. Coreopsis grandiflora and Coreopsis lanceolata live longer if divided every 2 to 3 years. |
Delphinium grandiflorum | Delphinium | 1 to 3 years | Spring | Fall-dug plants often die over winter. Regular division can prolong their life. |
Dendranthema x grandiflora | Garden Mum | Every year | Spring | Will survive longer and be most vigorous if divided and replanted every spring. Discard central core. |
Dianthus spp. | Pinks | 1 to 3 years | Spring | Dividing every few years can often extend longevity. |
Dicentra spp. | Bleeding Heart | 6 to 10 years | Spring | Cut crown apart with sharp knife. Roots are brittle, so handle carefully. |
Dictamnus albus | Gas Plant | 10+ years | Divisions are difficult due to crown damage. A spade plunged straight down through the plant's center, cutting the roots cleanly without severe bruising gives best results. | |
Dodecatheon meadia | Shooting Star | Fall (or Spring) | ||
Echinacea purpurea | Purple Coneflower | 4 to 5 years | Spring (or Early Fall) | Can remain undisturbed for years. Divide every 4 to 5 years for plant's health. Cut crown apart with sharp knife. |
Echinops ritro | Globe Thistle | 6 to 10 years | Spring (or Fall) | Resents disturbance. |
Epimedium x rubrum | Red Barrenwort | 6 to 10 years | Spring or fall | If conditions are favorable, can be left undisturbed for years. |
Eupatorium purpureum | Joe Pye Weed | 1 to 3 years | Spring to Summer/Early Fall | Use knife to slice woody crown. |
Euphorbia polychroma | Cushion Spurge | 10+ years | Spring (or Fall) | Discard central woody clump. Roots of some spurges are brittle, so handle carefully. |
Gaillardia x grandiflorum | Blanket Flower | 3 to 5 years | Spring or Fall | Divide by hand. |
Galium odoratum | Sweet Woodruff | Spring (or Fall) | Divide by hand. | |
Geranium spp. | Cranesbill | 6 to 10 years | Spring (or Early Fall) | Some varieties can be pulled apart by hand while others will need to be cut apart with a sharp knife. |
Geum triflorum | Prairie Smoke | 1 to 3 years | After flowering in late Summer | |
Grasses | Spring | Most grow well for years without division. Discard old, central portion of crown. Use sharp knife or spade to divide smaller grasses; use hatchet or ax on large grasses | ||
Gypsophila paniculata | Baby's Breath | 10+ years | Deep taproots resent disturbance. Double-flowered cultivars are grafted and, therefore, cannot be divided | |
Helenium autumnale | Sneezeweed, Helen's Flower | 1 to 3 years | Spring (or Fall) | |
Helianthus spp. | Sunflower | 1 to 3 years | Spring or Fall | Regular division improves performance and keeps invasive nature under control. |
Heliopsis helianthoides | False Sunflower | 5 to 10 years | Spring (or Fall) | Cut crown apart with sharp knife. Discard old central portion. |
Helleborus orientalis | Lenten Rose | 10+ years | Spring | Divide while plants are in bloom or immediately after they stop flowering. |
Hemerocallis spp. | Daylily | 3 to 5 years | Spring or immediately after flower | Division promotes heavier bloom. |
Heuchera sanguinea | Coral Bells | 1 to 3 years | Spring (or Fall) | Cut crown apart with sharp knife. Discard old, woody, central portion. |
Hibiscus moscheutos | Rose Mallow, Hibiscus | 10+ years | Spring or Fall | Plants are slow to send up shoots in spring, so fall division might be easier. |
Hosta spp. | Hosta | 6 to 10 years | Spring or Fall | If center of plant begins to get bare, cut out center and discard. |
Hyssopus officianalis | Hyssop | Spring | Carefully divide woody roots. | |
Iris spp. | Bearded Iris | 1 to 3 years | 4 to 6 weeks after flowers are finished blooming | Fewer blooms indicate need for rejuvenation. Use a sharp knife to cut rhizome. Discard older part of plant. |
Iris siberica | Siberian Iris | 6 to 10 years | Spring* or Late Summer/Early Fall** | *In spring divide before leaves are 3" to 4" tall. Dividing too late can stop bloom for an entire season. **In early fall, cut leaves back to 6" to 12" and then divide. Use sharp knife to cut rhizome. |
Lamiastrum galeobdolen | Golden Deadnettle | Spring or Fall | ||
Lamium maculatum | Spotted Dead Nettle | 4 to 5 years | Spring | Can also be divided mid-summer if cut back and watered well while taking root. |
Lathyrus latifolius | Perennial Sweet Pea | 10+ years | Spring | Does not like to be disturbed. |
Leucanthemum x superbum | Shasta Daisy | 1 to 3 years | Spring (or Fall) | Regular division can extend their life. Discard old central portion. |
Liatris spicata | Blazing Star, Gayfeather | 3 to 5 years | Spring | Cut into sections with sharp knife. |
Ligularia spp. | Ligularia | 6 to 10 years | Spring or Fall | |
Lilium | Lily | Late Summer / Early Fall | There are so many types of lilies, a whole book could be dedicated to how to divide each type. | |
Limonium platyphyllum | Sea Lavender | Spring or Early Fall | Carefully divide long roots. | |
Linum perenne | Flax | 10+ years | Spring (or Early Fall) | Does not like to be disturbed. Dividing long, tangled roots is chancy. |
Liriope spicata | Creeping Lilyturf | Spring or Fall | Use division to keep invasive nature under control. | |
Lobelia cardinalis | Cardinal Flower | 1 to 3 years | Spring or Fall | Discard old central, woody clump. |
Lupinus 'Russell Hybrids' | Russell Hybrid Lupine | 10+ years | Spring | Does not like to be disturbed. |
Lysimachia spp. | Loosestrife | 6 to 10 years | Spring (or Fall) | |
Malva alcea 'Fastigiata' | Hollyhock Mallow | 1 to 3 years | Spring or Fall | |
Matteuccia pensylvanica | Ostrich Fern | Spring | ||
Mentha spp. | Mint | 3 to 5 years | Spring or Fall | Use division to keep invasive nature under control. |
Mertensia virginica | Bluebells | 3 to 4 years | Spring | |
Monarda didyma | Bee Balm | 1 to 3 years | Spring | Discard old central clump. |
Myosotis spp. | Forget-me-Not | Spring | Divide by hand. | |
Nepeta spp. | Catmint | *Spring | Cut into sections with sharp knife or spade. * Can also be divided after primary bloom period if cut back and watered carefully. | |
Oenothera spp. | Sundrops, Evening Primrose | *10+ years | Spring (or Fall) | Most species do not divide well. Oenothera fruticosa needs to be divided every 1 to 3 years. |
Onoclea sensibilis | Sensitive Fern | Spring (or Fall) | ||
Osmunda spp. | Fern - Cinnamon | Spring | ||
Pachysandraterminalis | Japanese Spurge | Spring | ||
Paeonia sp. | Peony | 10+ years | Early Fall Mid-August / September | Does not like to be disturbed. Dig around plant & slit roots with sharp spade. Roots are thick and brittle. Replanting too deep can diminish flowering. |
Papaver orientale | Oriental Poppy | 6 to 10 years | Mid- to Late Summer | Resents disturbance. |
Penstemon digitalis | Smooth Penstemon | 1 to 3 years | Spring | Divide with spade or pitchfork. |
Perovskia atriplicifolia | Russian Sage | 10+ years | Spring or Fall | Does not like to be disturbed. |
Phlox paniculata | Tall Phlox | 2 to 4 years | Spring (or Late Summer) | Discard central core if woody or dead. |
Phlox subulata | Creeping Phlox | 1 to 3 years | Spring or Early Fall | Use only non-woody stems. |
Physostegia virginiana | Obedient Plant | 1 to 3 years | Spring | |
Platycodon grandiflorus | Balloon Flower | 10+ years | Spring | Does not like to be disturbed. Will not bloom for a year or two after division. Handle brittle root system carefully. |
Polemonium coeruleum | Jacob's Ladder | 6 to 10 years | Spring | Divide by hand. |
Polygonatum odoratum | Solomon's Seal | 6 to 10 years | Spring or Fall | Slice through knobby rootstock with knife. |
Polygonum cuspidatum | Fleeceflower | Spring or Fall | ||
Primula sp. | Primrose | Spring after flowering or Early Fall | Divide by hand. | |
Pulmonaria spp. | Lungwort | 6 to 10 years | Spring after flowering (or Fall) | Water regularly following division |
Pulsatilla vulgaris | Pasque Flower | 10+ years | Spring or Fall | Does not like to be disturbed. Fragile roots may die if bruised. |
Rheum palmatum | Ornamental Rhubarb | Spring | Use sharp knife to cut rootstock. Make sure each division has a dormant eye (crown bud). | |
Rudbeckia spp. | Black Eyed Susan | 4 to 5 years | Spring (or Fall) | Divide with spade or pitchfork. |
Salvia spp. | Sage | 6 to 10 years | Spring (or Fall) | When plant dies out in center, it's time to divide. |
Sanguisorba obtusa | Burnet | 4 to 5 years | Spring or Late Summer | |
Saponaria ocymoides | Soapwort | Any time during warmer months | ||
Scabiosa columbaria | Pincushion Flower | 4 to 5 years | Spring | Division is a reliable but slow method of propagation. |
Sedum spp. | Stonecrop | 4 to 5 years | Spring | Divide by hand. |
Sempervivum tectorum | Hen & Chicks | Spring or Fall | Separate small outer rosettes from parent plant. | |
Sidalcea spp. | Dwarf Hollyhock, False Mallow | 1 to 3 years | Spring or Fall | |
Solidago spp. | Goldenrod | 4 to 5 years | Spring or Fall | Divide with spade or pitchfork. |
Stachys byzantina | Lamb's Ears | 4 to 5 years | Spring (or Fall) | Divide by hand. |
Tanacetum coccineum | Painted Daisy | 1 to 3 years | Spring or Late Summer | |
Thalictrum spp. | Meadow Rue | 6 to 10 years | Spring | Most species are slow to recover after division. |
Thermopsis spp. | False Lupine | 10+ years | Spring | Resents disturbance. Only divide when plants are several years old. |
Thymus spp. | Thyme | 4 to 5 years | Spring | |
Tiarella wherryi | Foamflower | 1 to 3 years | Spring (or Fall) | Divide by hand. |
Tradescantia x andersoniana | Spiderwort | 3 to 5 years | Spring (until flowers set) | Division is only way to ensure duplication of cultivars. |
Tricyrtis hirta | Toad Lily | 6 to 10 years | Spring | |
Trillium grandiflorum | Trillium | 10+ years | Spring or Late Summer | Does not like to be disturbed. |
Trollius chinensis | Globe Flower | Fall | Slow to recover from transplanting. | |
Veronica spp. | Speedwell | 3 to 5 years | Spring or Early Fall | |
Veronicastrum virginicum | Culver's Root | 4 to 5 years | Spring or Late Summer | |
Vinca minor | Periwinkle | Spring or Fall | ||
Viola spp. | Violet | Spring or Fall | Divide by hand. | |
Waldsteinia ternata | Barren Strawberry | Spring (or Early Fall) | Division is safest when plant is not blooming. | |
Yucca filamentosa | Adam's Needle, Ivory Tower, Yucca | 10+ years | Resents disturbance. Divide only young plants. Established plants have deep, thick roots. |