How to divide perennials

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How to divide perennials

How to divide perennials

Last Updated on March 6, 2020 by John

If you have healthy perennials it’s important to divide them regularly just to make sure they continue to perform as well the following year. This is something that is quite easy to do and it’s perfect for all clump-forming herbaceous perennials even plants like ornamental grasses.

Most perennials will do much better if you divide them every 2 or 3 years. If you want to increase how many plants you have in your garden by way of division, of course, you can do this on an annual basis. Some plants that do well when divided include agapanthus, lily of the valley, Delphinium, geranium, Daylily, Iris, ornamental grasses, Salvia, and more.

When to divide perennials

You can successfully divide your perennials at almost any time of the year as long as you keep them well watered after division. However, the most successful times of the year will be when your plant is not actively growing.

If you have a perennial that flowers in the summer, you should divide it between March and May or between September and November. Just make sure that the soil is dry enough that you can easily work with it. If you have a particularly wet Autumn, for example, wait until spring to divide. If you have a slightly tender or weak plant, spring is a better time anyway.

Iris flowering

If you have a spring flowering plant like an iris, it’s better to wait until June through August to divide the plant because this is when they are done flowering but they are ready to produce new roots.

How to divide your perennials

Dividing perennials can be quite simple. You start by gently lifting the plant out of its home with a garden fork or trowel is there not too large, working your way outward from the centre of the crown and never digging right at the base otherwise you will damage the roots. Once you’re able to pull the plant out, shake off any excess soil until you can see the roots quite well. 

There are some plants that produce individual plantlets which you’ll notice when you pull them out and if yours is one of these, you can simply tease out the plantlet and then separate it, and replant it.

when and how to divide a hosta plant
when and how to divide a hosta plant

Smaller, fibrous-rooted plants like hosta can be gently pulled apart once you lift them out of the ground. This will give you easily recognizable small clumps that you can replant.

If you have a fibrous root and perennial that’s quite large in size like the day lily you might need to garden forks that you use back-to-back in order to lift it out of the ground. Use them like you would a lever to loosen the dirt around the roots and then to break the root mass into different sections.

You can break it up into two sections or more depending on how many divisions you want to propagate.

In certain cases if your plant is too large you might need an axe or a sharp knife to cut your clump into two sections. If you have a woody crown like the Helleborus or fleshy Roots like the Delphinium you’re definitely going to need to the knife or the Spade to cut the clump in two different shoots. When you do that, try to cut it in two divisions that contain at least for healthy shoots.

Caring for the divisions

Once you divide your perennials important that you plant them as soon as possible and that you water them well so that they can get situated into their new home. You can replant them in the same location just to increase the number of plants you have in a small garden area where you can move them to a new part of the garden, alternatively, you can even put them in pots.

Exceptions to the rule

There are of course exceptions to the aforementioned rule. In some situations, you might need to use a slightly different technique. If you have a diorama or a Crocosmia, these need to be removed without any damage, which means you have to dig at least 30cm down to avoid touching the corms, and then remove the plant. The roots come in what look like chains and these can be individually separated or replant it intact. Any of the corms you see that are old, why isn’t, or disease should be done away with.

Hostas are another exception to the rule. With these, you can follow the same steps listed above but you can split large clumps into two sections that contain five shoots. If you have a cultivar that has fleshy roots you want to tease them apart by hand before you divide them.

Potential problems

Make sure that you replant your divisions very quickly. If you leave them out they can dry out and then they won’t be able to re-establish themselves.

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