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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.

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