Dividing Perennials

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:

1. Dig up the parent plant using a spade or fork.
2. Gently lift the plant out of the ground and remove any loose dirt around the roots.
3. 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.
4. Each division should have three to five vigorous shoots and a healthy supply of roots.
5. Keep these divisions shaded and moist until they are replanted.
6. When replanting be sure you dig your hole larger than the plants root system.
7. 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.
8. 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. Transplant