How To Cut Back Arborvitae – Restore Shape And Promote Thick Growth
To successfully prune your evergreens, focus on light thinning and shaping during early spring or mid-summer. Never cut back more than 25% of the green foliage in a single season.
The most critical rule is to avoid the “dead zone”—the leafless brown interior of the plant. Unlike many deciduous trees, arborvitae cannot sprout new growth from old wood, so cutting too deep will leave permanent bare spots.
We all appreciate the lush, year-round privacy that a healthy row of arborvitae provides to a landscape. These “trees of life” create a living wall that blocks wind, noise, and prying eyes while adding a classic structure to your garden.
However, many homeowners feel a sense of dread when these fast-growing evergreens begin to look shaggy or overgrown. You might worry that one wrong snip will leave a permanent brown hole in your beautiful Emerald Green hedge.
In this guide, I will show you exactly how to cut back arborvitae safely and effectively. You will learn the professional techniques to maintain their height, encourage dense foliage, and keep your plants thriving for decades.
Understanding Arborvitae Growth Habits and the Dead Zone
Before you pick up your shears, you must understand how these conifers grow. Arborvitae, specifically species like Thuja occidentalis, produce new growth only from the tips of their branches where green needles are present.
If you look inside the plant, you will notice a dark, brown interior area. This is known as the dead zone, and it occurs because sunlight cannot reach the center of the plant to support photosynthesis.
Unlike a boxwood or a privet, an arborvitae lacks latent buds on its old wood. If you prune back into this brown, leafless area, that branch will never produce green growth again.
This is why “topping” or heavy shearing can be so destructive. Always ensure you leave at least a few inches of green foliage on every branch you trim to ensure the plant can recover.
The Difference Between Cultivars
Different varieties require slightly different approaches. The popular Emerald Green (Smaragd) is naturally narrow and usually only needs light tip-pruning to keep it tidy.
The massive Green Giant arborvitae is a hybrid that grows much faster, sometimes up to three feet per year. These giants may require more frequent maintenance to prevent them from overwhelming a small yard.
Knowing your specific cultivar helps you predict its growth rate. This allows you to plan your pruning schedule before the plant becomes a structural problem for your home or power lines.
When Is the Best Time for Pruning?
Timing is everything when it comes to the health of your evergreens. The ideal window for how to cut back arborvitae is in the early spring, just before the new growth flush begins.
Pruning in late March or April allows the plant to use its springtime energy to quickly cover any cut marks with fresh, vibrant needles. This minimizes the time your hedge looks “worked on.”
A second, lighter pruning can be done in mid-summer, typically around late June or July. This is mostly for aesthetic shaping to keep the lines of a formal hedge looking sharp.
Avoiding Late Season Pruning
Avoid heavy pruning in the late autumn. Cutting back your plants in September or October stimulates new growth that won’t have time to “harden off” before the first hard frost.
This tender new growth is highly susceptible to winter burn. When cold winds hit these unseasoned tips, they turn brown and brittle, often requiring even more pruning the following spring.
If you live in a region with heavy snow, early spring pruning is also beneficial. It allows you to remove any branches that were bent or broken by the weight of the winter snowpack.
Essential Tools for Success
Using the right tools makes the job easier and ensures the health of the plant. Dull blades crush the wood fibers rather than slicing them, which creates an entry point for fungal diseases.
For small branches and detail work, a pair of high-quality bypass pruners is essential. Bypass blades act like scissors, providing a clean, surgical cut that heals quickly.
If you are managing a long hedge, electric or battery-powered hedge trimmers are a massive time-saver. However, they should only be used for light surface shaping, not for structural cuts.
- Bypass Loppers: For branches thicker than a pencil but less than two inches.
- Hand Shears: For manual, precision shaping of the outer foliage.
- Pole Pruners: To reach the tops of tall specimens without constantly moving a ladder.
- Disinfectant: A 10% bleach solution or rubbing alcohol to clean blades between plants.
Safety is also a priority. Always wear safety glasses to protect your eyes from falling needles and debris. Sturdy gloves will protect your hands from the slightly abrasive foliage and sticky resin.
How to Cut Back Arborvitae: A Step-by-Step Guide
Now that you have your tools and the timing is right, let’s walk through the process. Start by inspecting the plant for any signs of pest infestations, such as bagworms or spider mites.
Begin by removing the “three Ds”: wood that is dead, damaged, or diseased. These branches should be cut back to healthy wood or all the way to the main trunk if necessary.
Next, focus on thinning. Reach into the plant and remove a few of the larger branches that are crowding the interior. This improves air circulation and allows more light to reach the inner foliage.
Shaping for Sunlight
One of the most common mistakes is pruning the top wider than the bottom. This creates a “mushroom” shape that shades the lower branches, causing them to thin out and die over time.
Instead, prune your arborvitae into a tapered shape. The base should be the widest part, with the sides gently sloping inward toward the top, similar to an “A” or a pyramid.
This allows sunlight to hit the bottom of the tree just as much as the top. A well-tapered hedge will remain thick and green all the way to the ground for its entire life.
Managing Height
If your arborvitae is getting too tall, you can reduce the height, but proceed with caution. Locate the central leaders (the main vertical stems) and cut them back to a side branch.
Try to hide these cuts about 6 to 12 inches below the desired final height. This allows the surrounding side foliage to grow up and over the cut, concealing the blunt end of the trunk.
Remember the 25% rule here as well. If you need to remove four feet of height, consider doing two feet this year and two feet next year to avoid stressing the tree.
Common Pruning Mistakes to Avoid
The most heartbreaking mistake is “topping” an old arborvitae. People often do this when a tree has grown too large for its space, but it usually results in a flat, brown top that never regrows.
Another error is shearing too frequently. Constant shearing creates a very dense “shell” of foliage on the outside, which completely blocks light from the interior, making the plant hollow and brittle.
Avoid pruning when the foliage is wet. Moisture can spread fungal spores like Kabatina or Phomopsis blight from one branch to another, leading to widespread dieback.
Finally, never prune during a period of extreme drought or heat. The plant is already under stress and needs its foliage to regulate its temperature and moisture levels through transpiration.
Post-Pruning Care and Maintenance
Once you have finished cutting back your arborvitae, your job isn’t quite done. Pruning is essentially a surgical procedure, and the plant needs support to recover and grow.
Check the soil moisture. If the weather has been dry, give the plants a deep soaking. Water should reach at least 12 inches into the soil to support the root system.
Apply a layer of organic mulch, such as shredded cedar or pine bark, around the base of the trees. This helps retain moisture and keeps the roots cool during the summer heat.
Fertilization Needs
In the spring, consider applying a balanced, slow-release fertilizer. Look for an NPK ratio of 10-10-10 or 12-6-4. This provides the nitrogen needed for lush green needle production.
Avoid high-nitrogen fertilizers in late summer. You don’t want to force a flush of growth right before the winter dormancy period begins, as we discussed with winter burn risks.
If your soil is very alkaline, you might notice the needles turning yellow. In this case, an acidifying fertilizer or elemental sulfur can help the plant better absorb nutrients from the soil.
Dealing With Overgrown or Damaged Trees
Sometimes you inherit a property where the arborvitae haven’t been touched in a decade. In these cases, how to cut back arborvitae becomes a multi-year project.
If the trees are touching the house or hanging over a walkway, you can prune them back, but you must stop the moment you hit the dead zone. If that doesn’t clear the path, you may need to consider removal.
For trees split by heavy snow or ice, you can often save them using arborist tape or soft ties. Gently pull the split leaders back together and secure them; over time, the wood may heal and strengthen.
For severe damage, it is often better to replace a single tree in the hedge rather than trying to perform “miracle” pruning that will leave the plant looking permanently disfigured.
Frequently Asked Questions
Can I Cut My Arborvitae Back to the Trunk?
No. If you cut an arborvitae back to the trunk or into the brown interior wood, it will not regrow. You will be left with a permanent bare spot and an exposed trunk.
How Do I Make My Arborvitae Grow Thicker?
Lightly shearing the outer 1-2 inches of green growth twice a year encourages lateral branching. This makes the plant grow much denser and fuller over time.
Will a Topped Arborvitae Grow Back?
An arborvitae will not grow a new central leader once it has been topped. While the side branches will continue to grow upward, the tree will likely lose its natural conical shape.
My Arborvitae Is Turning Brown After Pruning; What Happened?
This is usually due to one of three things: cutting into the dead zone, pruning during a heatwave, or using dull, dirty tools that introduced a disease to the fresh cuts.
Conclusion
Learning how to cut back arborvitae is a vital skill for any homeowner who wants a beautiful, functional landscape. By respecting the dead zone and pruning with a plan, you can maintain the health and beauty of these evergreens for years.
Remember to work slowly, use sharp tools, and always aim for that tapered shape to keep the sunlight reaching every branch. Your patience will be rewarded with a thick, vibrant privacy screen that is the envy of the neighborhood.
Don’t be afraid to step back frequently during the process to check your progress. It is much easier to take a little more off than it is to wait years for a heavy-handed cut to grow back!
Taylor pairs an engineer's eye with years of hands-on work in soil, lawns and outdoor machinery. He tests ideas in his own garden, keeps tractors and mowers running himself, and speaks to local horticulture groups. Every Garden Aider guide is written to be practical, accurate and safe to follow.
“To bring life alive, you just need to mix some love with the compost, bedding, and gardening machines.”