How to Divide Plants – and Why You Should

| Care

Are you interested in some free plants to add to your landscape? There are plenty of them already all around you. In fact, many common landscape perennials can – and should – be divided. Dividing plants is easy. You just need to follow a few steps and become familiar with the types of plants which can be divided.

When perennial plants mature and increase in size, they can begin to overwhelm their space. Their vigor may even seem to fade somewhat, depending on their age. As perennials grow out from the center above and below ground, air circulation near the heart of the plant is reduced. This can create the potential for disease and pest issues. There’s an easy fix – and it creates more plants for you to give away to friends or plant in other garden beds.

 

Hosta

Hosta

 

What to Look For

So what does it mean to divide a plant? When you divide a plant, you dig it out of the ground and separate the parent plant into smaller sections. For many perennials – like hostas – it’s a good idea to divide every few years to maintain size and air movement and to rejuvenate the plant’s health.

Fall is the ideal time to divide most perennial plants, but allow four to six weeks for divided plants to establish before the ground freezes. By this time of year, active growth is waning, flowering is complete and the plants are settling into dormancy. Energy sources are diverted from foliage into roots and below-ground reserves. Since plants removed from the soil at this time don’t have the same energy demands as at other times of year, they can adapt more easily to being divided and replanted elsewhere.

Walk your landscape and look for good division candidates. Are there any garden areas that seem overcrowded? Did you notice any perennials that didn’t seem to put forth as much bloom this season? Below, I’ve included a list of common perennials to divide. If you’ve got any of the plants on this list, and they haven’t been divided in the past few years; those are a great place to start.

 

Black-eyed Susan

Black-eyed Susan

 

Getting Started

Before you get to work dividing, be sure to prepare the new planting area ahead of time. That will allow you to place the new sections into the ground right away before their root tissue dries out. One of the biggest enemies to successful division is the failure to replant the separated pieces before they dry out and become unviable.

There are several types of tools you can use: a sharp knife or machete, a flat shovel or spade, or a pair of spading forks (some roots will pull apart rather than needing to be cut).

Once you’ve got your tool of choice, dig around the plant and lift it from the soil. It will be pretty evident if the roots can be pried apart or if you will need to slice through them.

How-to Steps

A good-sized plant clump can be sectioned into multiple pieces, but it’s important to preserve as much root tissue as possible for each division (or section) that you will transplant.

It’s a good idea to start by cutting or pulling the parent plant in half or into thirds. Look for natural parts in the foliage to be your guide. Once you’ve made your first cut or two, you can examine the size of the clumps you have remaining and decide if those can be cut again into halves or thirds. Keep going until the remaining sections are small enough that further separation will remove too much root tissue.

Don’t be afraid to be a little rough with this exercise. Plants are much more resilient than we, as gardeners, tend to give them credit for. They will look a little “worse for wear” for a few days, but as long as they have sufficient root tissue left and you care for them properly (more on that next), they will rebound.

 

Asters

Asters

 

Getting Those New Plants Started

Plant your new sections into other garden beds or containers right away. Place them into the soil at the same level the parent plant was growing in its original location.

I prefer to enrich the soil with a handful of compost. Mix this around the root zone before setting the plant in place. The compost will improve the soil overall and slowly release nutrients to bolster plant health. Backfill the planting hole with the existing soil, and water thoroughly to hydrate the roots and eliminate air pockets.

An important finishing touch is to add about two inches of mulch around your new divisions. Mulch helps keep the soil moist, maintains better soil temperature consistency and reduces the chances of cold weather heaving.

Be sure to provide regular water for your transplants to help them establish during the next four to six weeks. They may look droopy for several days immediately following planting, but that’s not a sign they need water. In fact, expect it. Foliage dieback to the ground is a natural occurrence as herbaceous perennials enter dormancy.

In the spring, your new perennials should emerge as strong and viable plants.

Top Candidates for Division

Here is a list of some common perennials which can (and should) be divided:

  • Astilbe
  • Baptisia
  • Barrenwort (after they flower)
  • Black-eyed Susan (Rudbeckia)
  • Blanket flower (Gallardia)
  • Bluestar
  • Chrysanthemum
  • Columbine
  • Coralbell (Heuchera)
  • Daylilies
  • Fall aster
  • Garden phlox
  • Hardy fern (Japanese painted fern)
  • Hardy geranium
  • Hardy ginger
  • Hosta
  • Iris
  • Lenten rose (Hellebore)
  • Peony

 

Fern

Fern

 

There is also a short joe gardener How-to video, so you can watch as I divide some hostas in my landscape beds at the GardenFarm. I hope this helps you to spread some plant love – for free – in your landscape.

Links & Resources

Episode 011: Plant Propagation Basics – With Brie Arthur

Episode 014: Top Tips for Saving Money in the Garden

joegardenerTV YouTube: How to Divide Your Garden Perennial Plants

Growing a Greener World® Blog: Perennials in the Landscape

Thank you to Erica Glasener for her contribution to this post!

About Joe Lamp'l

Joe Lamp’l is the creator and “joe” behind joe gardener®. His lifetime passion and devotion to all things horticulture has led him to a long-time career as one of the country’s most recognized and trusted personalities in organic gardening and sustainability. That is most evident in his role as host and creator of Emmy Award-winning Growing a Greener World®, a national green-living lifestyle series on PBS currently in production of its tenth season. When he’s not working in his large, raised bed vegetable garden, he’s likely planting or digging something up, or spending time with his family on their organic farm just north of Atlanta, GA.

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