Dividing Perennials10/26/2012

How to Divide Perennials.


Dividing perennials is an easy chore for the home gardener.  The home garden benefits in two ways from dividing plants.  First; how to divide perennials depends on your intentions for the divided plants.  If your goal is to have two large plants that will bloom in a short time, then you want to divide your perennial into fewer divisions, meaning taking only one quarter of a large parent plant.   If however you want to yield a lot of new plants that you are patient about their size and can wait a season for their bloom time, then how you handle your division is much different. 

Division for a few large plants:

When you want to divide a large plant and yield another large plant that will quickly be established and bloom, take no more than one quarter of the original plant, and leave as much of the healthy roots intact as possible on the divided portion.  Use a trowel for a loose-knit plant like a coneflower.  A knife is better for perennials with a solid crown such as astilbe or peony.  A very heavy crowned plant such as a daylily will need a very sharp spade or two garden forks set back to back.  Keep in mind that old clumps of perennials are very heavy.  You may need some help to lever them out of the ground.

Division for many small plants:

Dividing large perennials into smaller perennials is a great way to get the mass plantings many people like.  When you want to get multiple divisions from one plant, you should first dig up the parent plant and cut off up to two thirds of the length of the lower roots.  Using a sharp knife cut the parent plant into 1 or 2 inch plugs (crowns) or individual fans (such as daylily or iris).  This method will yield many more plants however they will take longer to reach the blooming size of larger divisions.  Smaller plants require more care, and would do best if you pot them up to mature, then transplant them into the garden.

Some Helpful Hints:

1.        Prepare the new location for your divisions before you begin to divide your perennials.

2.       Remove the plant from the ground before you attempt to divide.

3.       Sharp tools will prevent damage to the roots and help them to be less susceptible to disease.

4.       Discard or compost the woody centers of old plants.

5.       Remove one-half to one-third of the foliage of your divisions to help the plant remain healthy, however do not remove more than that as you’ll slow growth and encourage rotting.

6.       Replant the divisions as soon as possible.  Do not allow them to dry in the sun.

7.       Plant the divisions a ½ inch higher than when originally planted.  This will allow for settling.

8.       Water new transplants well. 

9.       Shading new divisions for a week after planting.  You can do this by covering with moist newspaper or burlap held down by rocks or soil.

10.   Fertilize new divisions with either liquid seaweed or fish emulsions to provide trace elements and speed establishments.

11.   When dividing in the fall, heavily mulch the plants to prevent shallow freezing and frost heaving.

12.   For best results divide plants before the ground begins to get cold

13.   Some perennials do not like to be divided; these would be tap rooted varieties such as Asclepias tuberosa (butterfly weed).