Dividing Your Perennials: When, What and How

Fall Gardening| Perennials

Summer is winding down and with that comes the anticipation of fall.  Around here at FGS, we know that fall will be a busy time for us, and if you are thinking the same thing, you may want to get ahead on some of your garden tasks that need to be done late summer/early fall.  One of those tasks is dividing perennials. You might be thinking, “Do I have to?!” And the answer, most likely, is yes.  Perennials propagate and, often times, get “too big for their britches.” If the idea of doing that yourself leaves you feeling a little uncertain, we are here for you. In today’s post, we will take the mystery out of it and go over the when, the what and the how regarding perennial division.

Plan Ahead

Before you divide your perennials, make a plan for what you will do with each “new” clump.  You may want to relocate some to another area of your yard or garden. If this is the case, you will want to prepare that area before you start dividing.  You can store perennial clumps in a cool spot covered with damp newspaper until you are ready to plant. If you are thinking that you don’t have a spot in your garden for more perennials, consider giving them away to friends or local establishments (like churches or schools).  If you have an especially large amount that you don’t want, you may want to post on a popular classifieds sharing site (and maybe even make some money–just be safe :)).

The When

You can divide perennials most any time of the year (during the winter is not a great time). For most perennials, the late summer and fall is the best time to divide. Knowing the time is near, you may ask, “How do I know when my perennials are ready to divide?”  There a few tell-tale signs to look for that will help you know when to divide. Better Homes and Gardens suggests dividing perennials every 3-4 years (not a hard and fast rule, though). If you can’t remember when you planted your perennials, there are a few things to look for:

  • The clump has gotten larger than you want it or it seems overcrowded and/or overgrown.
  • Smaller leaves are growing in the middle of the clump and there are fewer flowers.
  • The clump has nowhere to grow except into one of its neighbors.

The What

To divide or not to divide?  That is the question.  While there are some perennials that don’t need to be divided, we have included a short list of popular perennials that should be divided when the time comes.  If you want a more exhaustive list, or don’t see the perennial you are wondering about, you will find a pretty exhaustive list here.  

  • Aster
  • Hosta
  • Yarrow
  • Lilies
  • Irises
  • Bee Balm
  • Blackeyed Susans
  • Peonies
  • Phlox
  • Coneflower

The How

The how is not quite as straightforward as the when and the what.  Some perennials are more particular about how they want to be divided them than others.  But many perennials can be divided using the following method:

Step-by-Step Instructions

1. Dig up the clump using a shovel or trowel.  If it is a very large clump of flowers (think huge clump of daylilies), a shovel like this one is great for getting deep enough to get all the roots.  You will want to push the shovel deep into the ground all around the entire perimeter of the plant.  

2. Using the shovel as a lever of sorts, you should be able to carefully lift the clump out of the ground.  If some of the roots break, don’t worry about it. Most perennials are very resilient.

3. Pull apart the large clump into smaller clumps.  Now, this is much easier said than done in some situations.  For many perennials, you will need to cut into the root ball with the shovel or even gardening saw to get the smaller clumps. Each clump should have some leaves and clumps of roots.  

4. Fill the hole that you created with compost so that the soil can be renewed and replenished, especially if you are planting some of the divided clumps there.  

5. You can rinse the roots off if you like, or if you’re ready to transplant immediately, you can just pop the small clump into the hole you have prepared.

6. When you are planting the new clumps, make sure that the hole is large enough for the roots to spread out. Fill the hole with a mixture of soil and compost to insure that the plant will have the nutrients it needs.   

7. Once you are finished planting, water your “new” plants well.  Save your fertilizer for the spring. 🙂

NOTE:  When you disrupt your happy little plants, they and their friends will go through a period of shock (wilting, drooping, etc..  Just be sure you have tucked them in nice and tight with soil, and don’t forget to water them while they re-establish themselves in their new home.

Dividing Irises

We are not going to get into specifics for each type of perennial, by any means, but a very popular perennial for our area is the iris.  And late summer (NOW) is the perfect time to divide them. Here are some tips for specifically replanting irises.

  • Iris roots are much more shallow than most perennials.  They usually grow only a couple inches or so below the soil.
  • Use a hand-tiller instead of a shovel to loosen the soil around the iris roots.  If you only have a shovel, that will work.  Just be careful.
  • Once you have them dug up, wash off the roots to expose them.
  • You can pull the roots apart to separate them, or even break or cut them.  You just need to make sure that each piece has a fan of leaves coming out of it. 
  • Trim the leaves back to about 3 inches or so and then you are ready to replant.  
  • Plant the roots in a shallow hole with leaves sticking out, cover with soil and compost mixture and then water.  

You’ve Got This!

We hope you have found this useful and that you have great success with dividing your perennials.  Know that we are here if you need help, and if you want to fill in some of the holes you create with new perennials, we have them in stock!  Happy digging and planting, friends!