What Perennials can be divided?
We love planting Perennials! Once established they are the perfect thing to fill the garden with beautiful blooms and foliage but, there may come a time when they outgrow their space and start taking over.
Some Perennials grow faster than others, and some can just get completely out of control with large root systems that steal water and nutrients from the plants around them. Dividing those Perennials not only control the size of the plant but will also encourage fresh new growth and as a bonus you now have additional plants to start a new bed or share with a friend!
Dividing plants is quite easy if you follow some simple guidelines.
The first step is knowing when to divide plants.
Plants should not be in bloom when they are divided as all of the plants energy needs to focus on re-establishing its root system.
Fall blooming hedge plants for Tennessee should be divided in the spring as the shoots begin to emerge. This lets you see exactly where to dig and the small emerging leaves will undergo less stress when the plant is moved.
Spring and summer blooming plants should be divided in the fall. Once the blooms have faded and the leaves begin to die back about six weeks before the ground freezes, it’s time to divide. At this point energy is going back to the roots, which is necessary for a successful transplant.
It’s best to do your dividing on an overcast day and if it hasn’t rained in a while it’s also a good idea to thoroughly water the plant the day before you’re going to dig it up. This will ensure the plant has adequate moisture as it undergoes stress.
When you’re ready to dig them up follow these simple steps:
- Dig up the parent plant using a spade or fork.
- Gently lift the plant out of the ground and remove any loose dirt around the roots.
- Separate the plant into smaller divisions by any of these methods:
- Gently pull or tease the roots apart with your hands;
- Cut them with a sharp knife or spade;
- Or put two forks in the center of the clump, back to back, and pull the forks apart.
- Each division should have three to five vigorous shoots and a healthy supply of roots.
- Keep these divisions shaded and moist until they are replanted.
- When replanting be sure you dig your hole larger than the plants root system.
- Use a good root stimulator/fertilizer at the bottom of the hole and back fill with loose soil so the roots don’t struggle to reach out.
- Be sure to water regularly until the roots begin to establish.
The Minnesota Extension office published a wonderful spreadsheet shown below, of common Perennials from the plant nursery with information on when to divide them as well as additional tips. With this information in hand you are ready to begin multiplying that Perennial collection!
|Common name||Scientific name||How often to divide||When to divide||Notes|
|Allium, ornamental onion||Allium spp.||Annually; as needed||Fall||Divide overcrowded clusters after foliage disappears. Plant “new” bulbs in fall.|
|Anemone||Anemone spp.||Rarely; every 10+ years||Spring||Does not re-establish well after being disturbed.|
|Artemisia||Artemisia spp.||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.|
|Aster||Aster spp.||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||Astilbe x arendsii||1 to 3 years||Spring or fall||Needs division for best bloom. Cut plant into sections with sharp spade or knife.|
|Balloon flower||Platycodon grandiflorus||Rarely; every 10+ years||Spring||Does not like to be disturbed. Will not bloom for a year or two after division. Handle brittle root system carefully.|
|Beardtongue, smooth Penstemon||Penstemon digitalis||1 to 3 years||Spring||Divide with spade or pitchfork.|
|Bee balm||Monarda didyma||1 to 3 years||Spring||Discard old central clump.|
|Bellflower||Campanula spp.||4 to 5 years||Spring or late summer||Cut thick, fleshy rootstock apart with sharp knife.|
|Black eyed Susan||Rudbeckia spp.||4 to 5 years||Spring or fall||Divide using a spade or pitchfork. Will re-seed.|
|Blanket flower, Gaillardia||Gaillardia x grandiflorum||3 to 5 years||Spring or fall||Divide by hand (vs. using a spade or pitchfork).|
|Bleeding heart||Dicentra spp.||6 to 10 years||Spring||Will seed. Cut crown apart with sharp knife. Roots are brittle, so handle carefully.|
|Brunnera, false forget-me-not||Brunnera macrophylla||6 to 10 years||Spring, late summer or fall||Cut rhizome with a sharp knife. Transplant dividions fairly deep into soil.|
|Bugleweed||Ajuga reptans||1 to 3 years||Spring or fall||Can be divided any time of year, but spring and fall are best for quick rooting.|
|Cardinal flower||Lobelia cardinalis||1 to 3 years||Spring or fall||Discard old central, woody clump.|
|Catmint||Nepeta spp.||Annually; as needed||*Spring||Cut into sections with sharp knife or spade. Can also be divided in spring after primary bloom period if cut back and watered carefully.|
|Cinnamon fern||Osmunda spp.||Annually; as needed||Spring|
|Clematis||Clematis spp.||Rarely; every 10+ years||Spring||Division recommended for only selected species. Cut crown apart with sharp knife or spade.|
|Columbine||Aquilegia spp.||Rarely; every 10+ years||Spring or late summer||Does re-establish well after being disturbed. Dig deep to get all tapering, finger-like roots. Cut young plant apart with a sharp knife.|
|Coral bells||Heuchera sanguinea||1 to 3 years||Spring or fall||Cut crown apart with sharp knife. Discard old, woody, central portion. Some plants can also be gently teased apart from each other.|
|Cornflower||Centaurea montana||1 to 3 years||Spring or fall|
|Cranesbill||Geranium spp.||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.|
|Daylily||Hemerocallisis spp.||3 to 5 years||Spring or immediately after flowerng||Division promotes heavier bloom.|
|Delphinium||Delphinium grandiflorum||1 to 3 years||Spring||Note that plants dug in fall oftern die over winter. Regular division can prolong the life of this plant.|
|Dwarf hollyhock, false mallow||Sidalcea spp.||1 to 3 years||Spring or fall|
|Echinacea, purple coneflower||Echinacea purpurea||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. Will seed – transplants will likely blom the second year.|
|False blue indigo||Baptisia australis||Rarely; every 10+ years||Spring||Difficult to re-establish. Dig deep to remove entire root system without breaking it. Cut crown apart with sharp knife or saw.|
|False lupine||Thermopsis spp.||Rarely; every 10+ years||Spring||Does not re-establish easily after division. Only divide when plants are several years old.|
|False sunflower||Heliopsis helianthoides||5 to 10 years||Spring or fall||Cut crown apart with sharp knife. Discard old central portion.|
|Foamflower||Tiarella wherryi||1 to 3 years||Spring or fall||Divide by hand.|
|Forget-me-not||Myosotis spp.||Annually; as needed||Spring||Transplant new planbts in spring. Divide by hand.|
|Goat’s beard||Aruncus dioicus||Rarely; every 10+ years||Spring or fall||Does not re-establish ealisy after division due to a deep rootstock. Use knife to cut woody crown.|
|Golden dead nettle||Lamiastrum galeobdolen||Annually; as needed||Spring or fall|
|Goldenrod||Solidago spp.||4 to 5 years||Spring or fall||Divide with spade or pitchfork.|
|Hen & chicks||Sempervivum tectorum||Annually; as needed||Spring or fall||Separate small outer rosettes from parent plant.|
|Hollyhock mallow||Malva alcea ‘Fastigiata’||1 to 3 years||Spring or fall|
|Hosta||Hosta spp.||6 to 10 years||Spring or fall||If center of plant begins to get bare, cut out center and discard.|
|Hyssop||Hyssopus officianalis||Annually; as needed||Spring||Dig up and carefully divide woody roots.|
|Iris – bearded, German||Iris spp.||1 to 3 years||4 to 6 weeks after flowers are finished blooming||Fewer 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 – Siberian||Iris siberica||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.|
|Jack-in-the-pulpit||Arisaema triphylla||Annually; as needed||Fall||Divide offsets when plant is dormant|
|Jacob’s ladder||Polemonium coeruleum||6 to 10 years||Spring||Divide by hand (no spade or fork).|
|Japanese painted fern||Athyrium niponicum||Annually; as needed||Spring or fall||Use sharp knife to cut rootstock.|
|Joe Pye weed||Eupatorium purpureum||1 to 3 years||Spring to summer or early fall||Use knife to slice woody crown.|
|Lady fern||Athyrium filix-femina||Annually; as needed||Spring or fall||Use sharp knife to cut rootstock.|
|Lady’s mantle||Alchemilla mollis||6 to 10 years||Spring or early fall||Cut crown into sections with sharp spade or knife.|
|Lamb’s ears||Stachys byzantina||4 to 5 years||Spring or fall||Divide by hand.|
|Lenten rose||Helleborus orientalis||Rarely; every 10+ years||Spring||Divide while plants are in bloom or immediately after they finish flowering.|
|Liatris, blazing star, gayfeather||Liatris spicata||3 to 5 years||Spring||Cut into sections with sharp knife.|
|Lily||Lilium||Annually; as needed||Late summer / early fall||There are so many types of lilies, a whole book could be dedicated to how to divide each type.|
|Lily of the valley||Convallaria majalis||Annually; as needed||Spring or after flowering||Division helps to keep the plant from taking over the garden bed.|
|Lungwort||Pulmonaria spp.||6 to 10 years||Spring after flowering or fall||Water regularly following division|
|Lupine – Russell hybrid||Lupinus ‘Russell Hybrids’||Rarely; every 10+ years||Spring||Does not like to be disturbed.|
|Maidenhair fern||Adiantum pedatum||Annually; as needed||Spring|
|Meadow rue||Thalictrum spp.||6 to 10 years||Spring||Most species are slow to recover after division.|
|Milkweed||Asclepias spp.||Rarely; every 10+ years||Spring||Difficult to divide and re-establish due to a deep brittle taproot. Dig deeply. Cut crown apart with sharp knife.|
|Mint||Mentha spp.||3 to 5 years||Spring or fall||Use 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).|
|Monkshood||Acontium napellus||Rarely; every 10+ years||Spring||Not easy to re-establish once disturbed. Due to poisonous nature of roots, use rubber gloves when dividing tuberous roots.|
|Mum – garden, hardy||Dendranthema x grandiflora||Every year||Spring||Will survive longer and be most vigorous if divided and replanted every spring. Discard central core.|
|Ornamental grasses||Annually; as needed||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.|
|Ostrich fern||Matteuccia pensylvanica||Annually; as needed||Spring||Use a sharp knife or pruner to cut apart the rhizome connecting the individual plants.|
|Painted daisy||Tanacetum coccineum||1 to 3 years||Spring or late summer|
|Peony||Paeonia sp.||Rarely; every 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.|
|Periwinkle||Vinca minor||Annually; as needed||Spring or fall|
|Phlox – creeping||Phlox subulata||1 to 3 years||Spring or early fall||Replannt only non-woody stems.|
|Phlox – tall||Phlox paniculata||2 to 4 years||Spring or late summer||Discard central core if woody or dead.|
|Pincushion flower||Scabiosa columbaria||4 to 5 years||Spring||Plants can be slow to re-establish, but will do so eventually.|
|Pinks||Dianthus spp.||1 to 3 years||Spring||Dividing every few years can often extend longevity.|
|Poppy – oriental||Papaver orientale||6 to 10 years||Mid- to late summer||Seeds 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.|
|Primrose||Primula sp.||Annually; as needed||Spring after flowering or early fall||Divide by hand.|
|Rockcress||Aubrieta deltoidea||Annually; as needed||Spring|
|Rose mallow, perennial Hibiscus||Hibiscus moscheutos||Rarely; every 10+ years||Spring or fall||Plants are slow to send up shoots in spring, so fall division might be easier.|
|Russian sage||Perovskia atriplicifolia||Rarely; every 10+ years||Spring or fall||Does not like to be disturbed, so transplanting can be challenging.|
|Sage||Salvia spp.||6 to 10 years||Spring or fall||Dividee when center of plant dies.|
|Sea lavender||Limonium platyphyllum||Annually; as needed||Spring or early fall||Carefully divide the long roots.|
|Sedge||Carex spp.||Annually; as needed||Spring||Divide with spade or pitchfork.|
|Sensitive fern||Onoclea sensibilis||Annually; as needed||Spring or fall|
|Shasta daisy||Leucanthemum x superbum||1 to 3 years||Spring or fall||Regular division can extend their life. Discard old central portion.|
|Sneezeweed, Helen’s flower||Helenium autumnale||1 to 3 years||Spring or fall|
|Solomon’s seal||Polygonatum odoratum||6 to 10 years||Spring or fall||Use a sharp knife to cut up knobby rootstock.|
|Speedwell||Veronica spp.||3 to 5 years||Spring or early fall|
|Spiderwort||Tradescantia x andersoniana||3 to 5 years||Spring up until flowers bud and start to bloom||Division ensures replication of cultivars|
|Spotted dead nettle||Lamium maculatum||4 to 5 years||Spring||Can also be divided mid-summer if cut back and watered well while taking root.|
|Stonecrop||Sedum spp.||4 to 5 years||Spring||Divide by hand.|
|Sundrops, evening primrose||Oenothera spp.||Rarely; every 10+ years||Spring or fall||Most species do not divide well. Oenothera fruticosa needs to be divided every 1 to 3 years.|
|Sunflower||Helianthus spp.||1 to 3 years||Spring or fall||Regular division improves performance and keeps this potentially aggressive plant under control.|
|Sweet woodruff||Galium odoratum||Annually; as needed||Spring or fall||Divide by hand.|
|Thyme||Thymus spp.||4 to 5 years||Spring|
|Tickseed, Coreopsis||Coreopsis||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.|
|Toad lily||Tricyrtis hirta||6 to 10 years||Spring|
|Trillium||Trillium grandiflorum||Rarely; every 10+ years||Spring or late summer||Does not tolerate disturbance well.|
|Wild ginger||Asarum spp.||6 to 10 years||Spring or early fall||Use sharp knife to cut rhizome.|
|Yarrow||Achillea spp.||1 to 3 years||Spring||Separate by cutting or pulling apart. Discard central woody core.|