How to divide perennial plants and split oversize shrubs

It’s easy to forget about perennials. They grow quite happily year after year without much help from you. But after a few years they get too big and overcrowded – time to divide the plant.

What does that mean?

Dividing perennials is simple – just dig up any large clumps of perennials, separate them and replant them elsewhere in your garden. You are getting extra plants for free!

Why do they need to be divided?

Perennials grow fast and can develop large clumps that are also prone to fungal infections and insect infestations. The plant may stop flowering and even die off in the centre of the clump – it gradually becomes less healthy. It may also encroach on neighbouring plants and damage them.

How do I know if my plant needs dividing?

• If the plant has outgrown its space in the garden and looks too big and overcrowded
• The plant is flowering less than before or producing smaller blooms
• Its growth in the centre is starting to die off, or the plant is growing less than usual

Hydrangea

When should I divide them?

That depends on the plant. Dividing a plant while it’s in bloom would be too stressful for the plant (and the gardener). For most perennials, the best time is spring, while they are still dormant.

But there are exceptions to the rule: spring-flowering perennials like iris and poppies can be divided in late summer or early autumn. And peonies, goatsbeard, foxtail lillies, bleeding hearts and butterfly milkweed hate to be moved or divided at all. You should only divide these when absolutely necessary, or you risk killing the plant.

What do I do?

It couldn’t be easier. Choose a day when it’s not frosty or waterlogged. Using an ordinary garden fork, go around the plants, teasing them out of the ground. Knock off some of the soil so the roots are clearly visible.

Now you need to divide them by the roots or bulbs. You can slice down through the root/bulbs using an old kitchen bread knife.

My top tip is to do this with two garden forks. Push them into the plant back-to-back in the spot where you want to divide it. Then simply push the handles together, separating the fork tines. That lever action separates the roots or bulbs where they are weakest, limiting the damage done.

Now what?

Now you have two options. You can either replant the clumps in your own garden, or you can share them with your neighbours or your family. This technique is perfect if you want to do some swapsies with your fellow gardeners – you should be able to get some goodies in return for your perennials.

How do I replant them?

Perennials are generally very hardy plants but dividing them can damage the roots, so give them a nice comfy cushion to grow new ones into. Dig a hole bigger than the root and add some soft peat-free compost and compound fertiliser. Put the plant in the hole and cover with soil, then firm them back in and water well. It’s that easy to spread the love!