If your arborvitae is looking overgrown or a bit ragged, knowing how to prune arborvitae is the key to restoring its shape and health. This essential step-by-step guide will walk you through the entire process, from timing to technique, ensuring you get beautiful results without harming your plant.
Pruning these popular evergreens might seem intimidating, but it’s a straightforward task with the right knowledge. Done correctly, it encourages dense, lush growth and maintains the classic, tidy form that makes arborvitae such a great landscape choice. Let’s get started with everything you need to know.
How to Prune Arborvitae – Essential Step-by-Step Guide
This main guide breaks down the pruning process into clear, manageable stages. Before you make a single cut, it’s crucial to understand the “why” and “when” behind the practice.
Why Pruning Your Arborvitae Matters
Pruning isn’t just about controlling size. Regular, light pruning promotes a thicker growth habit, as it stimulates new stems to sprout from just behind the cut. This prevents the thin, spindly look that can happen when they are left alone.
It also allows sunlight and air to reach the inner branches. Better airflow reduces the risk of fungal diseases, which can thrive in damp, stagnant conditions. Removing dead or damaged branches also stops problems from spreading and improves the plant’s overall appearance.
The Best Time to Prune Arborvitae
Timing is one of the most important factors for success. The ideal window is in late spring or early summer, just after the new, light-green growth (often called “candles”) has emerged but before it hardens off and turns darker.
Pruning at this time gives the plant the rest of the growing season to recover and produce new buds for next year. You can do a very light cleanup or shape-up in early fall, but avoid heavy pruning then, as new growth may not harden before winter frost.
Avoid pruning in late summer or fall. Cutting too late can stimulate tender new growth that will be killed by the first freeze, causing unnecessary stress and damage to the plant.
Tools You’ll Need for the Job
Using clean, sharp tools makes the job easier and is better for your plants. Dull tools crush stems, and dirty tools can spread disease. Here’s what to gather:
- Hand Pruners (Bypass Style): For cuts on small branches, up to about 1/2 inch in diameter.
- Hedge Shears (Manual or Electric): For shaping and trimming the green foliage on smaller varieties. Use these only on the soft, green growth.
- Loppers: For thicker branches, between 1/2 inch and 1.5 inches thick.
- Pruning Saw: For any rare, larger branches over 1.5 inches.
- Protective Gear: Safety glasses and sturdy gloves are always a good idea.
- Disinfectant: Rubbing alcohol or a bleach solution to clean your tools before you start and between plants.
Step-by-Step Pruning Instructions
Follow these steps in order for the healthiest results. Always step back periodically to check your progress from a distance.
Step 1: Inspect and Clean Up
Start by walking around your arborvitae. Look for any branches that are clearly dead, diseased, or broken. These should be your first removals.
Using your hand pruners or loppers, cut these damaged branches all the way back to the main trunk or a healthy lateral branch. Make your cut just outside the branch collar (the slight swelling where the branch meets the trunk). Don’t leave stubs, as they can rot.
Step 2: Thin for Health and Light
Thinning is about removing select branches to open up the plant’s interior. The goal is not to change its shape drastically, but to improve air circulation.
Identify areas that look overly dense. Choose a few of the older, inward-growing branches and cut them back to their point of origin on a main trunk. This selective removal allows light and air to penetrate, which is vital for the health of the inner foliage.
Step 3: Shape and Reduce Size
This is where you control the overall form. For a natural look, always trim the plant so that it is wider at the bottom than the top. This “A” shape allows sunlight to reach the lower branches, preventing them from browning out.
- Never cut back into the old, brown, leafless wood. Arborvitae often will not sprout new growth from these bare areas, leaving a permanent bald spot.
- Only trim the current year’s green growth, or the previous year’s growth at the very most. A good rule is to never remove more than one-third of the live foliage in a single year.
- Use your hedge shears or hand pruners to lightly shape, making many small cuts rather than a few large ones. This creates a more natural, soft appearance.
Step 4: The Final Check and Cleanup
Once you’re satisfied with the shape, do a final walk-around. Look for any missed dead branches or uneven areas. Tidy up any stray shoots that spoil the clean lines.
Rake up and dispose of all clippings, especially any that came from diseased branches. This helps prevent pests and diseases from lingering in your garden. Give the plant a good drink of water to help it recover from any stress.
Common Pruning Mistakes to Avoid
Even with good intentions, its easy to make errors that can set your plant back. Here are the big ones to steer clear of:
- Topping the Plant: Lopping off the entire top to reduce height is a disaster. It destroys its natural form and forces weak, unattractive growth.
- Shearing into Brown Wood: As mentioned, cutting beyond the green foliage leaves permanent holes. Always check that you are trimming only where there is live growth.
- Creating a “V” Shape: Trimming the plant so it’s narrower at the bottom than the top shades the lower limbs, causing them to eventually die back and turn brown.
- Over-pruning: Removing to much foliage at once shocks the plant. It can struggle to recover and become susceptible to other problems. Stick to the one-third rule.
- Using Dull or Dirty Tools: This seems minor, but it leads to ragged cuts and potential infection. Clean and sharpen your tools regularly.
Special Cases: Rejuvenating an Overgrown Arborvitae
If you’ve inherited a giant, overgrown arborvitae, don’t despair. While you can’t drastically reduce its size in one year, you can begin a multi-year rejuvenation plan.
Over three consecutive growing seasons, you can gradually reduce its size. Each spring, prune back slightly farther into the green foliage than you normally would, but never into completely brown wood. You may find some inner branches that still have green needles.
Combine this with selective thinning of older branches each year. This slow and steady approach encourages back-budding and can eventually restore a more manageable size and denser habit, though it requires patience.
Aftercare Following Pruning
A little care after pruning supports quick recovery. Water the plant deeply if the soil is dry, providing about an inch of water per week during dry spells. A layer of mulch around the base (but not touching the trunk) helps retain moisture and regulate soil temperature.
Hold off on fertilizing immediately after a significant prune. Let the plant focus on healing its cuts and producing new growth first. You can apply a balanced, slow-release fertilizer designed for evergreens in the next spring if needed.
FAQ: Your Arborvitae Pruning Questions Answered
Can you prune arborvitae in the fall?
Light shaping or cleanup can be done in early fall, but it’s not the ideal time. Avoid major pruning in fall, as it can promote new growth that won’t survive winter. Stick to late spring/early summer for the main pruning session.
How much can you cut back arborvitae?
As a general rule, never remove more than one-third of the total live green growth in a single year. Cutting back to far, especially into old wood, risks sections of the plant not growing back.
Will arborvitae grow back after cutting?
Yes, but only from areas that still have green needles or latent buds. If you cut a branch back into the brown, inner wood where there are no needles, it will not regrow from that point. New growth comes from the green, vegetative parts.
Why are my arborvitae turning brown after pruning?
Browning after pruning is usually caused by cutting into the old, non-productive wood. It can also be a sign of stress from over-pruning, or from using dull tools that damaged the branches. Sometimes, browning unrelated to pruning is caused by pest, disease, or winter burn.
What’s the difference between shearing and pruning arborvitae?
Shearing is just trimming the very outer surface to create a smooth, formal shape, often with hedge shears. Pruning is a more thoughtful process that involves selective removal of branches for plant health, structure, and size control. For best long-term health, use pruning techniques rather than just shearing.
How do you shape an overgrown arborvitae?
Shape an overgrown plant gradually over several years. Each season, trim back slightly further into the green growth while also thinning some inner branches. Accept that you may not be able to restore a perfect shape quickly, but you can improve it significantly with consistent, careful cuts.
With this guide, you have the confidence to approach your arborvitae pruning project. Remember the golden rules: prune at the right time, never cut into bare wood, and always maintain that wider-at-the-bottom shape. Your careful attention will be rewarded with healthy, vibrant, and beautifully structured plants that enhance your garden for years to come. Taking the time to do it right is always worth the effort.