Sue Hunter On Pruning Holly: Be Selective With Young Plants; Use Hat-Racking For Older Ones

TREES > HOLLY > PRUNING

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 boxed hedge or something approaching a topiary, holly lends itself well to being shaped and pruned.

Why Prune Holly?

“Holly is versatile in the garden and landscape – there is a species of holly for every situation,” claims Sue Hunter – President of the Holly Society of America.

This versatility also extends to their pruning needs.

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 Holly

Deciding when to prune comes down to finding the balance between convenience and the plant’s stage in its lifecycle.

The 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.

“Winter berries will also have been eaten by birds by this time, so leaving pruning until the spring will help them,” adds Roy Nicol, a Master Horticulturist.

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.

“Besides, the same issue arises where new growth is damaged by late frosts and sets the plant back at the start of the new season,” Roy says.

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 bud as possible.

Doing so will encourage the bud to grow, and is the quickest way to facilitate new growth on your holly tree.

Bear in mind that, according to Sue, pruning holly with shears is not always to best idea:

“Over time, shearing causes irregular growth within the branching structure of the plant which causes dieback from the inside out.”

How Far Can You Cut Holly Back?

“Younger hollies respond well to selective pruning as they grow, whilst old, established hollies respond well to a more drastic type of pruning called ‘hat-racking’,” explains Sue.

“Hat-racking is where most of the branches are reduced to one-third to one-half their original size and it is almost always performed during the winter dormancy.”

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.

“It can take two growing seasons for a Holly which has been hard-pruned to cover itself in foliage again, but it’s worth the wait, as the shrub will then be the desired shape and size and can be selectively pruned more regularly to keep it that way,” adds Roy.

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.

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 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.