Horticulture Magazine

How And When To Prune Holly Trees

holly branches and berries up close

Left to their own devices, most holly varieties will grow into a large tree shape. The maximum height will vary between varieties, with some able to reach fifteen metres or more.

Prune it, however, and you can sculpt your holly tree into completely different shapes. Whether a boxy hedge or something approaching a topiary, holly lends itself well to being shaped and pruned. This guide will teach you how to do it.

a large holly tree in a field
Holly, left alone, will grow into a traditional tree shape

What is holly?

In case you’re not familiar, let us briefly introduce holly.

As the common name for the ilex plant, holly refers to just shy of 500 species of plant. Ask most people to describe it and you’ll hear variations on the theme of “green and white spiky leaves”, “red berries”, and “everywhere at Christmas”.

This description does cover a lot of holly varieties, but there are plenty that sit outside of it. Some types are smooth, for example. Others have solid green leaves rather than green-white ones, and others still have a splash of yellow. Some types have green on the outside; others have it on the inside. And only the female bushes have berries!

And on the subject of berries: Holly berries are poisonous! Although they might look appetising, the bright red berries are harmful to humans and household pets alike. Don’t eat any, and if they are ingested, seek medical advice immediately. They’ll most likely cause gastrointestinal issues, but long-term damage is possible.

Why prune?

Some holly varieties grow to over fifteen metres high, meaning that they become quickly unruly – especially if they’re in an area of your garden where a giant tree won’t fit with the aesthetic.

Pruning is a great way to keep your tree in check, and to force its natural tendencies to comply with your aesthetic demands. Doing this properly won’t damage the plant, so make sure to read the following sections carefully. They’ll teach you what you need to know to keep your holly under control without causing any damage.

When to prune

Deciding when to prune comes down to finding the balance between convenience and the plant’s stage in its lifecycle. Consensus is that late spring, around April, is the best time, as the plant is most receptive to pruning, and the outdoor conditions are conducive to the job.

Pruning too late in the year can increase the risk of new shoots being young when the first frosts hit, leading to stunted ongoing growth. Pruning too early means you have to spend hours out in the cold fighting with a spiky bush, which isn’t our idea of fun.

ilex branches and berries covered in snow
Although it’s undeniably festive, pruning in these conditions is best avoided

Beyond those constrictions, you have a lot of flexibility with timing, but spring is favourite.

How to prune holly

Now you’ve got an idea of the best time to prune a holly tree, you need to know how to do it. There’s a little more to it than taking secateurs to the plant and going wild: You want to prune in a way that encourages new growth while respecting old growth, and avoiding damage to either.

The received wisdom is to prune stems rather than leaves, and to do this as close to a flowering bus as possible. Doing so will encourage the bud to grow, and is the quickest way to facilitate new growth on your holly tree.

How far back can you prune holly?

Theoretically you can prune back very hard, although bear in mind that the stems on the inner part of the tree may have much less growth than the outer ones. This is because, over time, they’ll have received less sunlight than the outer branches, meaning fewer buds and fewer leaves.

So, if you’re pruning back hard, you may encounter parts of the tree with relatively small amounts of growth. If these formerly inner branches become outer ones on your newly-pruned configuration, the tree may look more barren and bare than it did before.

This isn’t necessarily a problem, as these branches will start to put forth buds and leaves over time. You just have to accept that your holly tree may not look as healthy as it once did.

a holly hedge that has been pruned
A well-pruned wall of holly

What to keep in mind

Most holly is sharp! If you’ve ever trodden barefoot on a dried holly leaf, you’ll know just how painful their spikes can be. And obviously taking pair of secateurs to your holly tree involves putting your hands, arms, and even face very close to their treacherous barbs.

When pruning holly, make sure to wear the relevant gear. This obviously includes thick gloves, but we recommend wearing long sleeves and long trousers, too. Going pruning in shorts and a tee is asking for trouble (in the form of cuts, scrapes, and nicks).

Some gardeners advise wearing goggles when pruning holly, too. This may seem excessive, and you might feel like a bit of a wally heading into the garden in full protective clothing, but avoiding a spike in the eye when you’re looking up into your holly tree is worth the risk to your street cred!

Of course, if you’re growing a variety like Golden King whose leaves are wonderfully smooth, you can probably leave the riot gear indoors.

What about holly in containers?

One of the appealing things about holly is that it grows well in containers, making it a great ornamental plant for balconies, patios, and even indoor settings. Growing holly in containers requires more pruning, however, so don’t put those gloves away just yet.

When growing holly in a container you’ll want to prune it annually at first, gradually switching to twice a year in most cases once the plant is ready for it. And you’ll know when it’s ready, as it will take two prunes a year to keep it in the condition that one used to take.

Some holly varieties lend themselves to growing in containers. Myrtifolia Aurea Maculata is one example, reaching an agreeable maximum height of around three metres. Hascombensis is another good choice: its full height of about half a metre makes it an adorable option for growing in a pot.

Be holly jolly

Although holly is most strongly associated with Christmas here in the UK, making its way onto cards, adverts, wrapping paper, wreaths, and tons of other places, it really is a rewarding plant all year round. Kept under control, holly adds a lovely visual element to any outdoor space. Whether you’ve got a big, flourishing tree, a well-kempt bush, or an attempt at a shaped topiary, a well looked-after holly makes a bold statement.

This guide has taught you everything you need to know about keeping holly in check. We’ve covered everything from full-size trees to miniature holly varieties better suited to being grown in containers.

Whichever you go for, we wish you luck in keeping it looking fabulous. Just remember to be careful if you opt for a spiky variety!

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