Perennial Division Guide


False sunflowerHeliopsis helianthoides5 to 10 yearsSpring or fallCut crown apart with sharp knife. Discard old central portion.
FlaxLinum perenneRarely; every 10+ yearsSpring or early fallDifficult to re-establish after division. Dividing long, tangled roots is
 also difficult.
FoamflowerTiarella wherryi1 to 3 yearsSpring or fallDivide by hand.
Forget-me-notMyosotis spp.Annually; as neededSpringTransplant new planbts in spring. Divide by hand.
Gas plantDictamnus albusRarely; every 10+ yearsSpringDivisions 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. CAUTION: Wear gloves as contact may cause dermatitis.
Globe flowerTrollius chinensisAnnually; as neededFallSlow to recover after transplanting.
Globe thistleEchinops ritro6 to 10 yearsSpring or fallDifficult to re-establish.
Goat's beardAruncus dioicusRarely; every 10+ yearsSpring or fallDoes not re-establish easily after division due to a deep rootstock.
Use knife to cut woody crown.
Golden dead nettleLamiastrum galeobdolenAnnually; as neededSpring or fall
GoldenrodSolidago spp.4 to 5 yearsSpring or fallDivide with spade or pitchfork.
Hen & chicksSempervivum tectorumAnnually; as neededSpring or fallSeparate small outer rosettes from parent plant.
Hollyhock mallowMalva alcea 'Fastigiata'1 to 3 yearsSpring or fall
HostaHosta spp.6 to 10 yearsSpring or fallIf center of plant begins to get bare, cut out center and discard.
HyssopHyssopus officianalisAnnually; as neededSpringDig up and carefully divide woody roots.
Iris - bearded, GermanIris spp.1 to 3 years4 to 6 weeks after flowers are finished bloomingFewer blooms indicate need for rejuvenation. Cut groups of leaves back to
fan shape to reduce water loss. Use a sharp knife to cut the rhizome (root)
 into 3-4" sections with at least on fan of leaves and roots. Discard older
part of plant.
Iris - SiberianIris siberica6 to 10 yearsSpring* 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.
Jack-in-the-pulpitArisaema triphyllaAnnually; as neededFallDivide offsets when plant is dormant
Jacob's ladderPolemonium coeruleum6 to 10 yearsSpringDivide by hand (no spade or fork).
Japanese painted fernAthyrium niponicumAnnually; as neededSpring or fallUse sharp knife to cut rootstock.
Japanese spurgePachysandra terminalisAnnually; as neededSpring
Joe Pye weedEupatorium purpureum1 to 3 yearsSpring to summer or early fallUse knife to slice woody crown.
Lady fernAthyrium filix-feminaAnnually; as neededSpring or fallUse sharp knife to cut rootstock.
Lady's mantleAlchemilla mollis6 to 10 yearsSpring or early fallCut crown into sections with sharp spade or knife.
Lamb's earsStachys byzantina4 to 5 yearsSpring or fallDivide by hand.
Lenten roseHelleborus orientalisRarely; every 10+ yearsSpringDivide while plants are in bloom or immediately after they
finish flowering.
Liatris, blazing star, gayfeatherLiatris spicata3 to 5 yearsSpringCut into sections with sharp knife.
LigulariaLigularia spp.6 to 10 yearsSpring or fall
LilyLiliumAnnually; as neededLate summer / early fallThere are so many types of lilies, a whole book could be dedicated to how
 to divide each type.
Lily of the valleyConvallaria majalisAnnually; as neededSpring or after floweringDivision helps to keep the plant from taking over the garden bed.
LoosestrifeLysimachia spp.6 to 10 yearsSpring or fall
LungwortPulmonaria spp.6 to 10 yearsSpring after flowering or fallWater regularly following division
Lupine - Russell hybridLupinus 'Russell Hybrids'Rarely; every 10+ yearsSpringDoes not like to be disturbed.
Maidenhair fernAdiantum pedatumAnnually; as neededSpring
Marsh marigoldCaltha palustrisAnnually; as neededAfter flowering - May or June
MasterwortAstrantia spp.4 to 5 yearsSpring or fallDivide with spade or pitchfork.
Meadow rueThalictrum spp.6 to 10 yearsSpringMost species are slow to recover after division.
MilkweedAsclepias spp.Rarely; every 10+ yearsSpringDifficult to divide and re-establish due to a deep brittle taproot. Dig deeply.
 Cut crown apart with sharp knife.
MintMentha spp.3 to 5 yearsSpring or fallUse division to reduce aggressive spreading. Use a sharp knife or pruner to cut
apart stolons (creeping stems on the soil surface with roots and shoots).
MonkshoodAcontium napellusRarely; every 10+ yearsSpringNot easy to re-establish once disturbed. Due to poisonous nature of roots, use
 rubber gloves when dividing tuberous roots.
Mum - garden, hardyDendranthema x grandifloraEvery yearSpringWill survive longer and be most vigorous if divided and replanted every spring.
 Discard central core.
Obedient plantPhysostegia virginiana1 to 3 yearsSpringSpreads easily in moist soil conditions.
Ornamental grassesAnnually; as neededSpringMost 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.
Ostrich fernMatteuccia pensylvanicaAnnually; as neededSpringUse a sharp knife or pruner to cut apart the rhizome connecting the individual plants.
Painted daisyTanacetum coccineum1 to 3 yearsSpring or late summer
Pasque flowerPulsatilla vulgarisRarely; every 10+ yearsSpring or fallDoes not like to be disturbed. Fragile roots may die if bruised.
PeonyPaeonia sp.Rarely; every 10+ yearsEarly fall, mid-August / SeptemberDoes not like to be disturbed. Dig around plant & slit roots with sharp spade. Roots are thick and brittle. Replanting too deep can diminish flowering.
Perennial sweet peaLathyrus latifoliusRarely; every 10+ yearsSpringDifficult to re-establish after division.
PeriwinkleVinca minor Annually; as neededSpring or fall
Phlox - creepingPhlox subulata1 to 3 yearsSpring or early fallReplannt only non-woody stems.
Phlox - tallPhlox paniculata2 to 4 yearsSpring or late summerDiscard central core if woody or dead.
Pigsqueak, heart leaf BergeniaBergenia cordifolia4 to 5 yearsSpring or summerCut rhizome with sharp knife. Transplant divisions fairly deep into soil.
Pincushion flowerScabiosa columbaria4 to 5 yearsSpringPlants can be slow to re-establish, but will do so eventually.
PinksDianthus spp.1 to 3 yearsSpringDividing every few years can often extend longevity.
Poppy - orientalPapaver orientale6 to 10 yearsMid- to late summerSeeds if allowed. Transplants can be planted in the spring. Main plant does not like to be disturbed, so can be difficult to re-establish after transplant.
Prairie smokeGeum triflorum1 to 3 yearsAfter flowering in late summerYoung plants can be easily dug up and transplanted.
PrimrosePrimula sp.Annually; as neededSpring after flowering or early fallDivide by hand.
Red barrenwortEpimedium x rubrum6 to 10 yearsSpring or fallIf conditions are favorable, can be left undisturbed for years.
RockcressAubrieta deltoideaAnnually; as neededSpring
Rose mallow, perennial HibiscusHibiscus moscheutosRarely; every 10+ yearsSpring or fallPlants are slow to send up shoots in spring, so fall division might be easier.
Russian sagePerovskia atriplicifoliaRarely; every 10+ yearsSpring or fallDoes not like to be disturbed, so transplanting can be challenging.
SageSalvia spp.6 to 10 yearsSpring or fallDividee when center of plant dies.
Sea lavenderLimonium platyphyllumAnnually; as neededSpring or early fallCarefully divide the long roots.
SedgeCarex spp.Annually; as neededSpringDivide with spade or pitchfork.
Sensitive fernOnoclea sensibilisAnnually; as neededSpring or fall
Shasta daisyLeucanthemum x superbum1 to 3 yearsSpring or fallRegular division can extend their life. Discard old central portion.
Snakeroot, bugbaneActaea racemosa (formerly Cimicifuga racemosa)Rarely; every 10+ yearsSpringResents disturbance. Cut plant into sections with sharp knife or spade. Discard old, woody, central clump.
Sneezeweed, Helen's flowerHelenium autumnale1 to 3 yearsSpring or fall
Snow-in-summerCerastium tomentosum1 to 3 yearsSpring or fallCan be divided virtually anytime.
Snow-on-the-mountainAegopodium podagraria 'Variegatum'1 to 3 yearsSpring or fallCan spread quickly and become aggressive.
SoapwortSaponaria ocymoides Annually; as neededAny time during warmer months
Solomon's sealPolygonatum odoratum6 to 10 yearsSpring or fallUse a sharp knife to cut up knobby rootstock.
SpeedwellVeronica spp.3 to 5 yearsSpring or early fall
SpiderwortTradescantia x andersoniana3 to 5 yearsSpring up until flowers bud and start to bloomDivision ensures replication of cultivars
Spotted dead nettleLamium maculatum4 to 5 yearsSpringCan also be divided mid-summer if cut back and watered well while taking root.
StonecropSedum spp.4 to 5 yearsSpringDivide by hand.
Sundrops, evening primroseOenothera spp.Rarely; every 10+ yearsSpring or fallMost species do not divide well. Oenothera fruticosa needs to be divided every 1  to 3 years.
SunflowerHelianthus spp.1 to 3 yearsSpring or fallRegular division improves performance and keeps this potentially aggressive plant under control.
Sweet woodruffGalium odoratumAnnually; as neededSpring or fallDivide by hand.
ThriftArmeria spp.4 to 5 yearsSpring
ThymeThymus spp.4 to 5 yearsSpring
Tickseed, CoreopsisCoreopsis1 to 3 yearsSpring or early fallCut crown apart with sharp knife. Coreopsis grandiflora and Coreopsis lanceolata live longer if divided every 2 to 3 years.
Toad lilyTricyrtis hirta6 to 10 yearsSpring
TrilliumTrillium grandiflorumRarely; every 10+ yearsSpring or late summerDoes not tolerate disturbance well.
TurtleheadChelone spp.4 to 5 yearsSpringWhen young offshoots are 1" high, dig with spade to sever from parent plant.
VioletViola spp.Annually; as neededSpring or fallDivide by hand.
Virginia bluebellsMertensia virginica3 to 4 yearsSpring
Wild gingerAsarum spp.6 to 10 yearsSpring or early fallUse sharp knife to cut rhizome.
YarrowAchillea spp.1 to 3 yearsSpringSeparate by cutting or pulling apart. Discard central woody core.
Yucca, Adam's needle, ivory towerYucca filamentosaRarely; every 10+ yearsSpringResents disturbance, so divide only young plants. Established plants have deep, thick roots.

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