How to Divide Perennials

What is a Perennial?

Perennials are those garden staples that will come back year after year, and can handle our chilly (okay, sometimes ridiculously cold) winters. A perennial plant is one that has a long lifespan that can range, depending on the type of plant and variety, from a few years to indefinitely.

Why Divide a Perennial?

Over time in your garden plants will naturally grow and flourish with proper location and care. Sometimes you’ll need to step in and take action because,

• It might be getting crowded! Division can help plants get a little extra circulation to reduce the chance of disease. 
• It might be dead in the middle. The growth habit of some plants promotes new growth on the outside of the plant, and the interior of the plant may die off as it ages.
• They get too big for the space you planted them in. If you’re lucky, your happy plants will grow to their full potential, but they might outgrow the garden bed you planted them in and they’ll need to be thinned.
• Sharing is caring! One of the most fun reasons is to make more plants to fill in your gardens or to share! When plants are a mature size it doesn’t hurt to divide them and share a piece with a friend or neighbour. 

When is the best time to divide a perennial?

A general rule we endorse for dividing plants is do it when the weather is cooler and they’re not in bloom. This would mean a spring or summer bloomer, like peonies and irises would be divided in the fall, and fall bloomers such as rudbeckia and sedum get their turn in the spring. 

However, if you have to divide during blooming or in the middle of the summer, your plant might still make it if you can give it some shade for the first day or two, and water it really well for the first few weeks.

Many gardeners will tackle division after the first couple frosts as plants will be entering dormancy and are less likely to notice the disturbance until next spring! 

How to Divide a Perennial

Before you begin, just remember that most plants are pretty tough and gardening is an art, not a science. The room for error is thankfully pretty high, and you don’t have to be too delicate. 

• Prep your plant by cleaning up any dead leaves or stems. If dividing in the fall, trim back any excess leaves to make it easier to move and see what you’re doing.
• Dig around the outer growth of the plant (also called the drip line), lifting up slightly as you dig. 
• Lift the entire plant with a shovel and place somewhere that you can easily access the root ball. Take a quick look at the root system and remove any mushy or dead root sections you might find. 
• It’s time to do the actual division! Depending on the root systems, you can sometimes split with your hands by simply pulling sections apart. If the system is too tough or fibrous, lay the plant on its side and cut or split with a shovel or a garden knife.

Replanting Your New Plants

When you’re replanting your new divisions, ensure you don’t bury them deeper than they were when originally planted. You can also take this time to amend your soil if needed with some compost, manure or a sprinkle of bone meal and give your planty friend a good deep water to settle soil around the roots. As a helpful step you can add a layer of mulch (can be wood, straw or leaves) to help retain moisture, but make sure to keep the mulch away from the crown/stem! It’s not necessary but definitely helps.

Plants That may Require Division

Many types of plants may require division at some point. Some of the most common are: