When to Divide Different Perennials

When to Divide Different Perennials

perennials

Spreading and creeping Perennials and Groundcover plants fill our gardens in lovely color! Sometimes they need some help keeping to their boundaries or preventing overcrowding and choking themselves (and sometimes other plants) out!

Some plants like your Hosta and Daylilies can successfully be divided and transplanted at any time throughout the growing season when the ground isn’t frozen. But some others are well… a bit more particular about the timing.

So when should you divide and transplant your garden lovelies?

Dividing and Transplanting Perennials

Generally speaking, fall-blooming Perennials get divided in spring, and spring-blooming Perennials get divided in the fall. Transplanting Perennials is about the same!

Generally…

spirea

This is because Ma Nature has rules, turns around and breaks those rules, makes new rules, breaks those, then ignores all her own rules and does whatever she wants.

Factoring in the resilience and adaptability of these types of plants, as long as you planted them in the right climate, the right amount of sun, and are there to water them - most will do fine no matter when you get them moved around!

Perennials are wonderful small flowering plants (and foliage plants too) that bring loads of color, vital nectar and pollen-rich flowers for pollinators, long-lasting or long-blooming flowers, and fresh growth throughout the growing season before typically dying back to their roots for the winter. Just to start it all over again next year…a bit bigger.

There are many good reasons to divide your Perennial plants:

  • Keep the plants healthy and vigorous
  • Increase air circulation around the plants
  • Maintain the size
  • Maintain the health of the roots
  • Prevents overcrowding
  • Break up larger clumps and spread them out throughout the garden and repeat them throughout your border.
  • Give some away as gifts and share the beauty!
  • Stimulates new growth

When Perennials have been growing in the same location for a few years (it’s recommended you divide them every 3-5 years) they can deplete the soil of nutrients, fill the soil area with dead roots and debris, push soil out away from the inner root clump (ever see what happens when you forget to repot that Spider Plant?) and generally have worn out their welcome in that area.

peony

By digging up these plants carefully, separating them into more modest-sized clumps, and replanting them elsewhere, you create more space for roots to grow and absorb nutrients and water.

It also provides you with the opportunity to replenish the original site with fresh earth, compost, and other amendments as needed.

Some Perennials like Peonies and Rhubarb have been well-known to grow undisturbed in the garden for 50 or more years!

Signs It’s Time To Divide

It’s recommended you divide your clumping perennials every 3-5 years. Some of the telltale signs it’s time to divide your perennial plants include:

  • Reduced or non-existent flowering displays
  • Yellowing leaves for no reason
  • Stunted, wimpy, sickly-looking growth
  • The center of the clumps is dying out/Bald spots
  • The clump is overtaking its area or overtaking other plants
  • Excessively leggy growth that needs staked when it didn’t in the past
  • Smaller flowers

How To Divide Perennials

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Some gardeners dig up the whole mother plant and divide it up. This gives you a clear picture of the entire root system you are working on and where best to divide it up.

*Tip: Always use sharpened and sterilized garden tools for this job!

Digging Up The Entire Plant

  1. Take stock of your Perennial in the ground, clear away leaf litter and mulch. Brushing away as much surface soil as possible to get a good idea of where the root ball extends.
  2. Using a sharp straight spade, push it down all around the Perennial root ball, just outside of its reach. Go as deep as you can with each push (usually about 1-2 feet depending on the size and type of perennial). If you are seeing cut roots after removing the shovel, back away a bit and continue.
  3. Using the shovel, spade, or garden fork, start going around the root ball and gradually begin lifting/separating it from the area. Work around the entire root ball lifting gently until it comes loose.
  4. Pull the root ball out and hose off excess soil for a clear view of the root system.
  5. Plan your cuts! Look for clumps that are either already pulling away from the main Mother plant (pups or daughter plants), or just divide them up into 6-12 inch chunks.
  6. Once you know how many plants you’ll be breaking the Mother Plant up into, go dig and prepare the sites for the soon-to-be-divided plants. Wrapping the exposed Mother Plant’s roots to keep them from drying out or being exposed to the sun.
  7. Using a clean, sharp spade or garden knife, carefully make your cuts from crown to bottom, working around larger roots to keep from disturbing them. You can also use two garden forks back to back to pull apart the sections. For more delicate/smaller perennials, you can even your hands to tease the roots apart.
  8. As you separate each section, keep it watered or wrapped to prevent the roots from drying out or being exposed to the sun.

Digging Up Sections Of The Plant

You don’t always want or need to dig up the entire plant! If it looks great and is just getting too big, you can use this method for nipping back sections from the Parent Plant without disturbing the entire root system. 

  1. Clear the area you are taking a section from of debris, leaf litter, and mulch to get a better view of the area
  2. Using a sharp spade, cut into the root ball straight down in a curve or ‘V’ shape and use the shovel or garden fork to gently pry it free.
  3. Repeat with other sections you wish to remove, working around the perimeter of the main plant.
  4. Wrap the newly removed sections to protect them
  5. Fill the hole with water, then refill the hole you’ve created around the Mother Plant with fresh soil and/or compost.
  6. Prep the area for the new divisions to be planted.

digging

By only digging down, removing a portion of the main plant keeps it smaller and more manageable. This is also the best method when working with plants with deep taproots and larger fleshy rhizomes or tubers

If you are not transplanting the divided Perennials elsewhere around your property. Wrap the roots in wet newspaper and a plastic bag (not the leafy tops since the excess moisture can lead to rot) and give them away to an eager friend, family member, or neighbor!

Schools, Churches, and Retirement homes are always great places to gift your excess divided plants too! Otherwise, a local plant club or Master Gardener in your area will be happy to take them off your hands.

Once you’ve divided up your Perennial, it’s time to Transplant it!

transplant

  1. Amend the site you dug up your current Perennial, and sprinkle in some Nature Hills Root Booster. If you are moving the Perennial from the area entirely, fill the hole in with topsoil.
  2. Plant a section of the newly divided Perennial, water it in very well, and ensure its roots are planted at the same depth they were previously - no deeper and no higher. Then backfill with fresh topsoil and tamp down.
  3. Repeat with the remaining sections you’ve divided!
  4. Top-dress all the new plants with a 3-4 inch deep layer of arborist mulch and/or compost
  5. Check them daily and water deeply using the Finger Test as needed. Those disturbed roots will take a few days to get over the shock.

It may take a few weeks depending on the climate and the weather for them to settle in and begin new root formation. If you are watering in the autumn, water until the ground freezes or there is a blanket of snow to insulate and hydrate them.

But as soon as the ground is exposed and not frozen, break out that hose!

Dividing and Transplanting in the spring and summer means being ready to water as soon as that Finger Test shows it needs it. Water deeply, ensuring you’ve saturated the entire root ball and not just the surface few inches.

When To Divide Specific Perennials

Avoid dividing a plant that is already stressed - like drought, physical damage, etc., but in cases like planted in the wrong location (too shady/too sunny) or the ground has poor drainage or is wet/flooded and the plant is suffocating, by all means, get it moved to a more appropriate location!

It’s also recommended you do not divide or transplant plants while they are flowering.

Perennials Typically Divided In Spring

Here is a short list of the main types of Perennials that do best being divided early in the growing season, typically just before or right when you see new growth sprouting out.

  • Aster
  • Bee Balm
  • Butterfly Weed
  • Chrysanthemum
  • Columbine
  • Coral Bells/Alumroot
  • Delphinium
  • Dianthus
  • False Indigo - After new growth
  • Foamy Bells
  • Goldenrod
  • Geum
  • Hardy Hibiscus
  • Hyssop (Anise Hyssop)
  • Indian Pinks
  • Japanese Anemone
  • Lamb’s Ears
  • Liatris
  • Loosestrife
  • Ornamental Grass
  • Penstemon
  • Red Hot Poker Plants
  • Most Rudbeckia
  • Russian Sage
  • Perennial Salvia/Perennial Sage
  • Scabiosa
  • Tall Garden Phlox
  • Yarrow

Plants that had fall seed heads you wanted to keep throughout the fall and winter as texture, bird seed, and interest can now be pruned and divided in the spring as well!

infographic

Perennials Typically Divided In Fall

Along with Perennials that flower in the early spring, these Perennials are usually divided in the autumn a few weeks before the ground freezes solid (hard freeze). Preferring to be dormant first so they will remain dormant all winter and work on getting those roots settled under a blanket of snow.

  • Allium/Perennial Onion
  • Asiatic Lilies (after foliage yellows)
  • Bellflower
  • Black Eyed Susan
  • Corydalis
  • Perennial Geranium/Cranesbill
  • Oriental Lily (after foliage yellows)
  • Oriental Poppy
  • Peony
  • Primrose
  • Sedum
  • Spiderwort
  • Tiarella

Trim back any excess leaf matter from the crown and cover it with a fresh layer of arborist mulch to protect it. Especially if those leaves showed any signs of powdery mildew or other fungal issues last growing season.

fall infographic

Perennials That Can Be Divided Spring or Fall

These are the Perennials that are just fine with being moved around and divided any time they are dormant in the early spring or late fall. Even tolerating being moved at any time during the growing season if the situation warrants it.

Transplanting in early spring or fall means no excess heat and sun and no drought to contend with, nor do the plants need to focus on actively growing above ground at this time - giving them plenty of time to work on just new root formation.

  • Astilbe
  • Bergenia
  • Blanket Flower
  • Catmint/Catnip/Calamint
  • Coneflower
  • Coreopsis
  • Creeping Phlox
  • Daisies/Shasta Daisies
  • Daylily
  • Foxglove
  • Gaillardia (Blanket Flower)
  • Goat’s Beard
  • Hellebores/Helleborus
  • Hosta
  • Lavender
  • Liriope (Lily Turf)
  • Lungwort
  • Obedient Plant
  • Sea Thrift
  • Verbena
  • Veronica

fall/spring info

Exceptions

  • Iris plants are an exception, preferring to be transplanted after flowering in the late spring/early summer.
  • Most Perennials with a central taproot do not like being disturbed. Sea Holly has a long taproot and the taproots that develop alongside the main shoot can be divided in the spring, but also divided in the summer.
  • Some plants like Horseradish are difficult to transplant because they will regrow from the smallest roots left in the ground. Be sure you want aggressive growers like these where you plant them the first time because they will be difficult to get rid of once established. Plant in enclosed garden sections, barrels above or buried into the ground, or contained in some way.
  • Avoid transplanting or dividing Balloon Flowers because their roots are brittle and do not like being disturbed.
  • Some plants such as Globe Thistle, Russian Sage, Candy Tuft, some Milkweeds, Goat’s Beard, Lavender, Baby’s Breath, and Baptisia can be tricky and resist transplanting and division due to their type of root system.

When in doubt, check with your local County Extension Office for information on specific types of Perennials!

Free Plants From Mature Perennials!

Like a reward for all the pampering and care you gave them, dividing your Perennials is rewarding! Your plant babies can often be divided into 2, 3, 4, or more new plants for you to share and spread the love!

How many plantlets you divide your main clump into is also determined by how long you want to wait for that new plant to grow back to its mature clump size. If you have the patience and want to turn that one large Daylily clump into a new edging row, you can do it - but it will take several years for those transplants to fill in.

This form of propagation keeps your Perennial healthy and your garden brimming! So get out there this spring and see which of your plants need some wiggle room!

Happy Planting!

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