How to Determine 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 common plants below, with the best times for dividing perennials, and how to do so.

Timing is Key When Dividing Your Garden Perennials

Timing and technique are so important when it comes time to divide perennials.

Many perennials can be divided in either early spring or early fall, but some plants can be very sensitive to when they should be split.

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I’m a self-taught hobby gardener, not a Master Gardener. Everything I share with you on my blog is my personal opinion and things that worked for me along the way.

Reasons to Divide Your Perennials…

Keeps the plant healthy by giving the plant more space for the roots to grow, and absorb nutrients and water.
Increases the number of flowering blooms.
Manages the size of the plant and keeps it from overcrowding others in the garden.
Keeps the plant from dying out in the middle and leaving a bare hole by dividing it every 3-4 years.
Creates more plants for future plantings in your garden and to share with others.

I’ve listed some of the most common garden perennials, and the most optimal times to divide them using the best methods for each.

Perennials to Divide by Hand

Plant	Season	Instruction
Bleeding hearts	Spring	Divide after the plant flowers
Dianthus	Spring, Summer	Mat-forming types root as they grow; cut a rooted piece from the edge and replant
Hellebore	Spring	Divide when plants are in bloom, or right after they stop flowering
Lady’s mantle	Spring, Fall	Easier to divide in early spring when you start to see the leaves emerge
Lamb’s ear	Spring, Summer, Fall	Roots are along the stem; cut a piece off the edge and replant; cut leaves back by half
Primroses	Spring	Transplant after the plant has finished blooming
Salvia	Spring, Fall	Divide every 5-6 years or when the plant dies out in the center; divide in the spring in cold and winter climates.
Yarrow	Spring, Summer	Easy to divide; most types spread quickly and should be divided every 2-3 years

Perennials to Divide With a Spade or Pitchfork

Plant	Season	Instruction
Anemone	Spring	Division is rarely needed, perhaps once every 8-10 years
Asters	Spring	Dividing in spring allows the new plants time to establish before the end of summer
Bee balm	Spring	Divide every 2-3 years in the early spring
Black-eyed Susan	Spring, Fall	Divide in either spring or fall
Catmint	Spring, Fall	Divide every 3-4 years in either spring or early fall
Coneflower	Spring, Summer, Fall	Divide every 4-5 years for healthier plants; reseeds and seedlings are easy to transplant
Daylily	Spring, Summer, Fall	Divide every 5-7 years; it’s better to lift rebloomers in spring before they flower
Garden mum	Spring	Divide every 2-3 years to keep plants blooming and vigorous; discard dead central portion
Phlox	Spring, Summer, Fall	Divide every 3 years or when flowering diminishes; discard the woody center and plant the edge pieces
Goldenrod	Spring, Fall	Divide every 3-5 years to keep plants vigorous
Hostas	Spring, Summer, Fall	Easy to divide in early spring when foliage is emerging;
Sedum Autumn Joy	Spring, Summer, Fall	Easiest to divide in spring when foliage is still small; dividing clumps later won’t harm the plant but may reduce bloom for the year
Shasta daisy	Spring, Summer, Fall	Easiest to divide in spring when foliage is still small
Yarrow	Spring, Summer	Easy to divide; most types spread quickly so divide every 2-3 years

Cut Up Rhizomes and Tubers With a Knife

Plant	Season	Instruction
Calla lily	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	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	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	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, but how the plant should be divided.

It’s so important to divide your plants to keep them healthy and increase the number 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.

I’d love to hear from you in the comments below.

Until next time,