The Best Time for Dividing Perennials

Do you often wonder whether you should be splitting and transplanting your perennials in the fall or the spring? I’ve created a guide that includes some of the more popular plants below, with the best times for dividing perennials, and how to do so.

Timing is Key

Timing and technique are everything when it comes time to dividing perennials. And while many perennials can be divided in either early spring or early fall, some plants can be extremely sensitive to when they should be split. I’ve listed the most optimal times to divide specific perennials below.

The Reasons to Divide Your Perennials…

• Keeps the plant healthy. It gives the plant more space for roots to grow and absorb nutrients and water.
• Increases the number of blooms.
• Manages the size of the plant and keeps it from overcrowding other plants.
• Dividing every 3-4 years will keep the plant from dying out in the middle, leaving a bare hole.
• Creates more plants for future plantings in your garden

PERENNIALS TO DIVIDE BY HAND

Plant name  Botanical name	Season	Instruction
Bleeding hearts Dicentra	Spring	Divide after the plant flowers
Dianthus Dianthus	Spring, Summer	Mat-forming types root as they grow; cut a rooted piece from the edge and replant
Hellebore Helleborus	Spring	Does not need to be divided often, but when you do, divide when plants are in bloom, or right after they stop flowering
Lady’s mantle Alchemilla mollis	Spring, Fall	Easier to divide in early spring as leaves begin to emerge; does not need to be divided often
Lamb’s ear Stachys byzantina	Spring, Summer, Fall	Roots are along the stem; cut a piece off the edge and replant; cut leaves back by half
Primroses Primula	Spring	Transplant after plant has finished blooming
Salvia Salvia	Spring, Fall	Divide every 5 or 6 years or when plant dies out in the center; divide in the spring in cold and winter climates.
Yarrow Achillea	Spring, Summer	Easy to divide; most types spread quickly so divide every 2 to 3 years

PERENNIALS TO DIVIDE WITH A SPADE OR PITCHFORK

Plant name  Botanical name	Season	Instruction
Anemone Anemone × hybrida	Spring	Division is rarely needed, maybe once every eight to 10 years. Transplanting should be done in the spring
Asters Aster	Spring	Dividing aster plants in spring will allow the new plants time to establish before the end of summer
Bee balm Monarda didyma	Spring, Fall	Divide every 2-3 years in the early spring
Black-eyed Susan Rudbeckia	Spring, Fall	Divide every 3 to 4 years; for best appearance next season, don’t make divisions too small
Catmint Nepeta × faassenii	Spring, Fall	Divide every 3-4 years in either spring or early fall
Coneflower Echinacea purpurea hybrids	Spring, Summer, Fall	Divide every 4 to 5 years for healthier plants; reseeds and seedlings are easy to transplant
Daylily Hemerocallis hybrids	Spring, Summer, Fall	Divide every 5 to 7 years; rebloomers are best lifted in spring before they flower
Garden mum Chrysanthemum hybrids	Spring	Easy to divide; divide every 2 to 3 years to keep plants blooming and vigorous; discard dead central portion
Garden phlox Phlox paniculata	Spring, Summer, Fall	Divide every 3 years or when flowering diminishes; discard the woody center and plant the edge pieces
Goldenrod Solidago	Spring, Fall	Divide every 3 to 5 years to keep plants vigorous
Hostas Hosta hybrids	Spring, Summer, Fall	Easy to divide in early spring when foliage is emerging; dividing large clumps later won’t harm plants but leaves them lopsided for the summer
Sedum Autumn Joy Sedum	Spring, Summer, Fall	Easiest to divide in spring when foliage is still small; dividing clumps later won’t harm plant but may reduce bloom for the year
Shasta daisy Leucanthemum x superbum	Spring, Summer, Fall	Easiest to divide in spring when foliage is still small; dividing clumps later won’t harm plant but will reduce bloom and leave plants lopsided for the year
Yarrow Achillea	Spring, Summer	Easy to divide; most types spread quickly so divide every 2 to 3 years

CUT UP RHIZOMES AND TUBERS WITH A KNIFE

Plant name  Botanical name	Season	Instruction
Calla lily Zantedeschia aethiopica	Spring	Most gardeners prefer to divide calla lilies in spring, especially in warm climates where you can leave the rhizome in the ground year round.
Dahlias Dahlia	Spring	In warmer climates where the tubers remain in the ground, you can dig up, divide, and replant the tubers in early spring. If you are overwintering tubers, you can divide in the fall.
Irises Iris	Fall	Using a knife or hands, break the rhizomes apart in groups of 1-3. Cut the foliage down by half with pruners.
Lily-of-the-valley Convallaria majalis	Spring, Summer, Fall	Rhizomes pull apart easily; make sure each new division has a leaf and a cluster of roots

I hope this gives you a better idea as to when the best time for dividing your perennials is. It’s so important to divide your plants for them to remain healthy and increased the amount of blooms. It also helps to keep your garden from overcrowding.

And my favorite reason for dividing perennials? They are the gift that keeps on giving year after year. I rarely have to go to the nursery and buy new perennials because I am constantly transplanting new plants throughout the garden.

Learn more about preparing your garden for winter.

Resources: Calla Lily Division and How to Divide Irises

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