How to prune buddleia – an expert guide to cutting your butterfly bush back and boosting those vibrant purple blooms

Don't be fooled by their easy breezy nature: if you want your butterfly bushes to look their best, you need to learn how to prune buddleia (also known as buddleja) like a pro. 

You've likely spotted the resplendent purple blooms of the buddleia popping up all over the place of late, and that's because this is one of the best plants for beginners: they really are that simple to grow, so long as you have a nice sunny spot for your butterfly bush. 

That being said, your buddleia will need at least a little TLC in the form of an annual pruning session, one of the plants to prune in February onwards, especially if you're hoping for plenty of purple blooms over the summer months. 

One thing to bear in mind? Just as there are countless ways to prune roses, depending on the variety you're working with, so, too, you must identify which type of buddleia graces your garden before you go to town with the pruning shears...

How to prune buddleja

Knowing which variety of this highly-favoured cottage garden plant you have is key to determining how to prune more efficiently. "It’s important to know which buddleia you are growing to know when to prune, which is very easy," promises Morris Hankinson, director of Hopes Grove Nurseries.

Explaining that buddleia davidii looks like the buddleia that "grows just about anywhere, even out of cracks of the pavement and along train tracks", Morris goes on to stress that this variety is available in many different colours, from dark purples and red to white, lilac and pink. 

"Buddleja alternifolia is slightly different with more arching, thinner stems," he continues, "while buddleia globosa has round orange flowers and is really quite striking."

It's a similar story when looking at how to prune clematis because there are several popular varieties and each method of pruning will differ depending on the flowering type.

Morris Hankinson

Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants. He established the thriving business in 1992, shortly after graduating with a Commercial Horticulture Degree from Writtle College, Essex. 

While there are other hybrids available as well, Morris adds that it's likely the majority of gardens will be graced by the not-so-humble buddleja davidii.

What you will need

You wouldn't start mowing your lawn or chitting your potatoes without the right gardening tools to hand, so be sure to prep accordingly before pruning your buddleja.

To that end, then, make sure you have:

• A pair of gardening all-purpose gloves
• A pair of bypass pruners
• A pair of bypass loppers

When to start the job

It's not just a case of learning how to prune buddleia; you need to know when to tackle the job, too – which, as you've likely already come to suspect, shifts depending on the variety you have at home.

"Buddleia alternifolia and globosa flower on stems from the previous season, so you should only ever remove oldest stems during midsummer," says Morris. "The aim with this is just a simple tidy, so you keep the shape of the bush."

If you're working with a buddleia davidii, however, your plant's pruning needs are going to be... well, they're going to be a bit more intense. As a result, you'll "need to schedule a hard pruning session every year between February and April," says Christopher O'Donoghue, one of the co-directors of Gardens Revived.

"The aim is to get to work before any new growth begins," he adds.

That's right: your buddleia absolutely belongs on your list of plants to prune in March, so be sure to wrap up warm and show it the love it deserves.

Christopher O'Donoghue

A gardener with over a decade of experience under his belt, Christopher set up Gardens Revived with his brother, Andrew, in 2018  to create a thriving family business. Together, they have worked on residential gardens, listed buildings and gardens, flower shows and large estates with some exceeding 70 acres – many with historical significance.

Step-by-step guide

Bold, beautiful blooms are one of those garden trends that never go out of style, especially now we're being encouraged to look after pollinators as much as we possibly can.

Learning how to prune buddleia is, thankfully, an easy way to boost your plant's blooming potential – not to mention help your butterfly bush do what it does best: keep butterflies well and truly sated with its rich supply of pollen.

1. Give your buddleia a good, hard prune

Using a pair of sharp, clean loppers (blunt, dirty blades are a surefire route to damaging your plant or, worse, spreading disease), you'll want "to cut your butterfly bush down to about 30cm from the ground, just above one bud or shoot," says Morris. 

"If you want your buddleia to grow tall, be sure to prune back to about 60cm from the ground,'" he adds, noting that larger stems may need to be removed with a pruning saw.

2. Use your secateurs to address the finer details

When pruning your buddleia, the aim (as always) is to "remove dead or damaged wood," says Christopher.

Morris agrees, adding that, should you "notice any dead stems, crossing branches or old dead smaller stems, you should use secateurs to prune these off and as far back as possible to avoid disease."

3. Maintain an open centre

If you're still sussing out how to prune buddleia, it's worth noting that you don't just want a low framework of stems: you also want to "maintain an open centre to improve air circulation," says Christopher.

4. Go for a hard prune

Just as you should do with your roses, the aim is to cut your buddleia bush back by a third.

"Cutting back a buddleia hard can look really quite brutal and you might wonder if it will ever grow back again," admits Morris, "but buddleia will soon grow new shoots and be in good shape with plenty of flowers the same year."

He adds that, if you want to extend flowering for later in the year, they can also be pruned during May to help pollinators later in the year.

FAQs

When should buddleia be pruned?

As most buddleja will flower on the branches that grow in early summer, you're best off pruning them before any new growth appears – between late February and mid-April.

How do I make my butterfly bush bushy?

"Buddleia davidii can grow very big and spread very easily so it’s important to keep in good shape and health," says Morris. "hey tolerate a hard prune, in fact, it’s better that you do, otherwise they can end up with a lot of straggly wood and a few flowers at the top."

He adds that as well as deadheading any spent flowers, a good hard pruning "between February and April will mean that you see more flowers at all levels of the plant, which is much more attractive".

Now that you know how to prune buddleia, you can rest assured that your butterfly bush will be the envy of all who see it. Which is, let's face it, the main reason we all garden in the first place, right? Happy pruning.