Cutting Back Leylandii Trees & Shrubs: When and How To Do It

Are you considering planting or have already planted leylandii trees or hedges in your yard?

If so, you’ve probably figured out that you need to learn about trimming or shaping them, including when and how to do it correctly.

Can I cut back leylandii? Leylandii trees and hedges can and should be cut back each year, typically in the spring or summer while there is plenty of time for its root system to recuperate and start growing again before the winter. Trimming the hedge down to less than 4 inches of greenery isn’t recommended.

Below, we’ll walk through the process of cutting back leylandii trees and hedges, and you’ll find helpful tips on trimming and techniques to avoid.

Shaping & Pruning Leylandii

Cutting the tops off of your leylandii trees and hedges is necessary for properly shaping them, especially during the first year of growth.

During the second and third years of growth, the side areas require extra attention when pruning.

In the long-run, the best practice is lightly pruning the tops and sides of the trees a minimum of 2 to 3 times per year.

Spring, summer, and autumn are the best times of the year for shaping and pruning leylandii hedges.

In the following sections, we’ll discuss each aspect of leylandii pruning and shaping in greater detail.

Can Leylandii Be Shaped?

Leylandii can be shaped into hedgerows in the same manner that other trees and shrubs can. All it takes is practice, persistence, and patience.

For new trees, heavy pruning may be required on the tops and sides depending on the exact shape and size you desire.

After the third year of regularly pruning, your leylandii should more or less keep its shape on its own. All you’ll need to do is continue light trimming sessions in the spring and fall each year.

Benefits of Pruning Leylandii

The benefits of pruning your leylandii trees or hedges are many:

Removing dead and broken branches promotes new growth.
Pruning reduces the likeliness of accidental property or bodily damage.
Pests (both insects and animals) are less likely to infest your hedges/trees if they are pruned regularly.
Promotes your tree’s natural shape (or keeps the shape of your hedge nice and neat).
Pruned materials may be recycled into high-grade organic mulch or compost.

When To Cut Back Leylandii

The very best times of the year to cut back leylandii are mid to late spring, summer, and early fall.

When you cut your leylandii during these times of the year, there is enough warmth, moisture, and sunlight for them to bounce back before the cold weather sets in for the winter.

In addition, there are some times that cutting back the leylandii trees or hedges can’t wait:

When branches pose a breaking/falling threat that may cause damage to people passing by or property.
When the hedges or trees are impeding a neighbor’s driveway, sidewalk, or view.
When the hedges become overgrown, too tall, too wide, or full of dead branches.

How To Prune Leylandii

Pruning leylandii evergreen trees and hedges is a straightforward process:

Using sharp pruning shears or an electric hedge trimmer like this 22-inch dual-action trimmer, cut back broken, dying, and dead branches off first
Trim the top of the hedges 4-6 inches below your desired height.
Prune the sides of the hedgerow or around the tree, reducing overgrown branches.
Take a step back and inspect your handiwork; trim any problem areas you notice.
Collect your clippings/branches, and mulch them or otherwise dispose of them.

How Hard Can You Prune Leylandii?

Leylandii branches may be trimmed 4 inches or so at a time without causing the tree harm. Just be sure to not cut back into bare or old wood as the tree will not regrow greenery from old wood.

Keep in mind that the maximum legal height of leylandii in most states is 6.6 feet tall – that’s pretty short.

Topping Leylandii

During the first year of caring for your leylandii, you’ll need to top them down to the desired height.

After that, you should give them a year or two to start producing thick healthy growth before topping them again.

Once your leylandii is over five years old, topping them once every one to three years is ample enough. Spring and fall are the best times for topping leylandii.

Best Time of Year To Cut Back Leylandii

Spring and summer are by far the best times of the year to cut back leylandii hedges and trees.

Later autumn and winter months should be avoided because they may be too late in the year for new growth to occur before the leylandii goes dormant for the winter.

Will Leylandii Grow Back After Cutting?

Most times leylandii grows back even thicker than it was before cutting. However, if the branches are broken off or trimmed too short, they may not have the means to regrowth themselves.

For that reason, make sure to leave at least 4 or 5 inches of length on the branches you prune.

Can You Keep Leylandii Small?

Leylandii, technically speaking, may be pruned, shaped, and kept at any size. Despite the myth that these often “giant” hedges can’t be kept small, they really can.

All you need to do is prune them an extra time or two per year if you want to keep your leylandii smaller than usual.

**When Not To Trim Leylandii**

Leylandii evergreens are hardy trees that can handle even excessive pruning, making them excellent hedges, but even these robust hedgerows have their limits.

Avoid trimming leylandii in the late autumn, winter, and early spring.

These times of the year don’t ensure enough warmth or moisture for the leylandii to start growing again before the freeze settles in for the year.

**What Not To Do When Pruning Leylandii**

Pruning leylandii, like most evergreen species often used for hedges, is rather simple (as outlined above).

That said, there are a few things you want to avoid when pruning these trees and hedges:

Snapping branches by hand.
Using an ax or hatchet to cut branches.
Cutting greenery down to less than 4 inches in length.
Cutting back to bare wood.

Tips for Pruning & Shaping Leylandii

When you’re ready to prune and shape your leylandii, here are a few tips to keep in mind:

Start with the obvious problem areas, like dead and broken branches.
Topping isn’t always necessary; don’t trim the top unless it needs it.
Keep the sides nice and neat; prune them two to three times per year.
Avoid mixing the cuttings/branches with your regular compost (they are acidic).

A Final Word

Leylandii trees require one to two prunings per year to keep a natural shape and maintain healthy growth. Hedgerows of leylandii need a bit more pruning and shaping, approximately three trimmings per year.

Start by cutting back the top, and then move on to trimming the sides up. For the best results, repeat the process every spring, summer, and early autumn.