Fall Home Improvement Section--Dividing Perennials

Ruth Brumit-Master Gardener Volunteer

September 13, 2002

There comes a time in the life of perennials when they outgrow their place. They may begin to show signs of being overcrowded by losing vigor, failing to flower as prolifically as they once did or dying out in the center.  This is normally the time to revive the plant by digging it up and dividing it.  Many hesitate to dig up a mature plant, but generally perennials benefit from being lifted and divided.  This is also a great way to control overly aggressive perennials.  The rule of thumb is perennials should be divided every three to five years.  Late summer or early fall is the ideal time to divide spring or summer blooming perennials.

The first step when dividing perennials is to decide which plants need to be divided this year, and how many new plants you wish to get out of the division.  The next step is to decide where your new plants will go; how many will be replanted, and how many will be traded, sold or given away.  Some perennials are patented (as indicated on the plant label when you purchased it, making it illegal for gardeners to sell the new plants produced by division.  The day before division, thoroughly water the plants. This water will help loosen the soil and hydrate the root system.  Divide your perennials on a cool cloudy day if possible and have a bucket of water handy.   

Before dividing, prepare the flowerbed where the new divisions will be placed.  Amend planting beds with a mixture of ground pine bark, leaf compost and Permatill.  Replanting as soon as possible increases the survival rate.  If you must hold the newly divided plants for a short period of time keep them cool, shaded and moist.

Most divisions can be done using a spade and either two garden forks or a large butcher knife.  I have even used a large screwdriver.  Begin by cutting around the outer perimeter of the plant with the spade.  Then, loosen the plant with a garden fork, lift the clump out of the ground and remove most of the soil from the roots.  The purpose for removing the soil is to make it easier to see the individual plants within the clump. 

Divide fine rooted perennials such as lambs ears by hand, gently teasing apart the clump into separate plants.  Divide tough or fleshy rooted types, such as hosta, by cutting down through the roots with a spade or butcher knife; or use two garden forks back to back to pry the clump apart. 

Once the clump has been divided, observe the central part of the plant (plant crown) and discard any portion that is severely injured or appears unhealthy.  Trim all broken and straggly looking roots.  This will stimulate the fibrous feeder roots to grow.  Plants with large amounts of foliage may also need to have some leaves pruned after they are divided, since there are now fewer roots to sustain the large leaf system.  Soak the root system of the new divisions in the bucket of water for about an hour and water thoroughly immediately after replanting in the new location.  Replant coral bells, peonies and iris slightly below soil level and all other perennials at the same level they were growing at before.

The ultimate goal of dividing perennials is to rejuvenate the health of the plant; however, dividing perennials pays dividends to the gardener.  It is often a way to get free plants for your own flowerbeds and extras to share with friends and family.  My personal favorite is swapping with other gardeners for other perennials or other varieties of the same perennial.  The Rowan County Master Gardener Association holds a plant sale and swap each May.  Many attend each year as it is a lot of fun and a good way to meet other gardeners and obtain new plants.