When & How To Divide Perennial Plants

How To Divide Perennials

Perennial plants come back year after year, that does not mean we can leave them to it, in fact, dividing a perennial can become necessary. Dividing perennials is a great way to multiply the plants in your garden but is also often necessary to keep a plant healthy and full of vigour.

What may seem like a pretty harsh or even destructive process dividing plants every 2 or 3 years actually encourages a perennial plants growth and stops them from becoming patchy and sparse.

Why Divide Perennials?

Garden Borders Perennials

There are a few good reasons why you would want to divide perennial plants. Not only is the process helpful to the gardener but also to keep the plant looking at it’s best. Here are a few of the reasons why you may want to divide a perennial.

The Plant Begins To Grow Poorly

You may notice after a few years a perennial will develop a bald spot in the crown, the blooms may be smaller or the plant will fail to flower at all and the plant is more prone to falling over and need extra support. If this is the case, dividing the plant into two more even more will make each division much healthier and more floriferous.

Manage The Size Of A Plant

When a perennial begins to get unruly, crowding out nearby plants it can be of benefit to divide at this point, whether you intend to use the division or not. Returning the plant back to a manageable size as well as stimulating new growth.

Increase The Number Of Plants For Free

The obvious benefit of dividing a plant is you can quickly fill out a border, move a particular plant around the garden and have more of that plant whether you think is suitable and it is completely free. Dividing a plant doesn’t mean just splitting it into two, you can get 4, 5 or 6 plants depending on the size of the plant being divided.

When To Divide Perennials?

You can divide perennial plants at any time as long as they are well looked after after division. It is, however, beneficial and more practical to divide plants when they are less active, i.e. not flowering or putting out new growth.

To work out when it is best to divide perennials we just need to know when they usually flower.

Dividing Spring Flowering Perennials

Early and spring flowering perennials should be divided after they have flowered as this is when they are putting out new roots. 

Once you have enjoyed the flowers and they have died back you can lift the plant and divide it around July to August. This will leave plenty of time for the new divisions to take root in their new place.

Dividing Summer Flowering Perennials

Summer and Autumn flowering perennials can be divided usually at 2 points in the year depending on when they are flowering or the conditions.

Spring between March and May when new growth occurs is one time and the other is in Autumn between September and November. This will, of course, be dictated according to whether the plant flowers in early or late summer. 

How To Divide Perennial Plants

Dividing a perennial is pretty straight forward. A little care is needed to avoid disturbing the root structure when lifting the plant and also to determine where the healthy divisions can be made.

Lifting Perennial

Look to make divisions that include 5 to 7 healthy shoots from the base of the plant, groups of shoots like this will then grow on to make healthy new plants.

To lift the plant using a fork and work around the plant taking care to remove as much of the root ball in one piece as possible.

Left the plant from it’s hole and remove as much of the excess soil as possible again taking care to leave the root structure intact.

Now with the plant out of the ground you can begin to divide the plant into separate pieces. Depending on the root structure, whether it is a woody plant or the density will determine the best way to do this, you can try the following methods:

Using Your Hands: If the root structure is fairly delicate then you may be able just tease apart divisions using your fingers, look to make divisions of 5 or so shoots and gently coax apart the roots to make the divisions.

Using 2 Forks or Spades Back To Back: For plants with a sturdier structure then teasing apart the roots may be too difficult, in these instances then the best option is to use either two forks or to spades. Push the tools back to back through the centre of the root ball and then lever the roots apart. This technique should enable you to get the roots and plant apart and looks a bit brutal but one the divisions are made the plants will be perfectly happy.

Knife, Axe or Lawn Edger: For really stubborn and woody roots then cutting is the only real option to make divisions. A  bladed tool such as a half moon edging tool or even an axe or knife will cut through the root and enable you to make divisions.

Dividing A Primrose

Caring For The New Perennial Divisions

Once you have made your divisions they need to be planted in their new homes straight away.

You may want to put one of the divisions back into the original position and this would be a good time to add some compost as the root ball will be smaller. 

Each plant can then be planted into the new spot and watered in well. Ensure that the new plants do not dry out until they are established.

If you are dividing the perennials in the late autumn, another option would be to pot them up and overwinter them in a sheltered spot. The plants can then grow and establish in the pots and be planted in the spring into the garden.

Leave a Comment

Your email address will not be published. Required fields are marked *