Topping an arborvitae means cutting the central leader and upper branches back to a uniform height, and while it will make the tree shorter in the short term, it comes with serious trade-offs. Arborvitae (Thuja) are conifers, and conifers generally do not regrow from old, bare wood the way many deciduous shrubs do. Cutting into leafless interior wood often leaves permanent bald spots, a flat and unnatural silhouette, and a weakened tree prone to disease and splitting. That said, there are ways to reduce an arborvitae’s height without destroying it, and there are situations where careful topping is the least bad option. The key is understanding what the tree can and cannot recover from before you pick up the shears.
Why Topping Is Risky for Arborvitae
Arborvitae grow from their tips. The green, scaly foliage you see on the outside of the tree is where active growth happens. Behind that green shell, the interior branches are mostly bare wood with little or no foliage. When you top an arborvitae by lopping off a large portion of the crown, you expose that bare interior. Unlike a hedge privet or a willow, arborvitae cannot push new growth reliably from old, leafless wood. If you cut back into a section that has no green foliage remaining on it, that section will likely stay bare.
The result of aggressive topping is a tree that looks like a flat-topped stump with brown, dead-looking sides near the cut. Over time the remaining branches may fill in somewhat, but the tree rarely returns to a natural shape. Topped arborvitae also tend to develop multiple weak leaders where one strong leader used to be. Those competing stems are structurally weaker, and in heavy snow or ice they split apart, sometimes destroying the tree entirely.
There is also a health cost. Large pruning wounds on conifers heal slowly and create entry points for fungal infections. Arborvitae are relatively tough trees, but a major topping cut removes a huge percentage of the tree’s food-producing foliage all at once, which stresses the root system and lowers the tree’s ability to fight off pests and disease.
When Topping Might Be Your Only Option
Sometimes the tree is already too tall and there is no alternative. Power line clearance, a neighbor dispute, local ordinance compliance, or a tree that has grown into the eaves of a building can all force your hand. If the arborvitae must get shorter and removal is not on the table, a modified topping approach can minimize damage.
The critical rule is this: never cut back farther than the point where live green foliage exists on the remaining branches. If you can see green growth six inches below where you plan to cut, the tree has a reasonable chance of recovering. If the nearest green growth is two feet below your cut line, that branch will almost certainly die back, and you will be left with a gap.
For most arborvitae, this means you can realistically take off about one to two feet of height without crossing into bare wood. Taking off three or more feet at once is where the damage becomes severe. If the tree needs to come down by several feet, doing it in stages over two or three years gives the tree time to push new growth closer to the cut line before you cut again.
How to Reduce Height Without Flat-Topping
The best approach for reducing an arborvitae’s height is not a flat horizontal cut across the top but rather a technique sometimes called “drop-crotch pruning” or “reduction pruning.” Instead of shearing the top off in a straight line, you selectively cut each upper branch back to a lateral (side) branch that is growing in a direction and at a height you want. The lateral branch you cut back to should be at least one-third the diameter of the branch you are removing. This lets each cut terminate at a living growth point rather than at bare wood.
Here is how to do it in practice:
- Identify the leader: Find the single central stem that extends to the very top. This is the branch doing most of the upward growing.
- Pick your target height: Look for a healthy lateral branch growing outward at approximately the height you want the tree to be. This lateral will become the new top.
- Make the cut: Using sharp bypass pruners, loppers, or a pruning saw (depending on the diameter), cut the leader just above the junction with that lateral branch. Do not leave a long stub above the lateral.
- Reduce surrounding branches: The branches near the former top will now stick up above your new height. Cut each one back to its own lateral, working your way around the tree so the silhouette tapers naturally rather than ending in a flat plane.
The goal is a slightly rounded or pointed top that looks like a shorter version of the tree’s natural shape, not a hedge-trimmer buzz cut. This takes more time than running a hedge trimmer across the top, but the tree recovers better and the result looks dramatically more natural within a single growing season.
Timing Matters More Than You Might Think
Arborvitae are evergreen, so people sometimes assume they can be pruned any time. Technically you can make cuts year-round without killing the tree, but timing affects how well and how quickly the tree fills back in.
Late spring through early summer, after the first flush of new growth has started to harden off, is the best window. At that point the tree is actively growing, has energy reserves from the spring push, and has the entire rest of the growing season to produce new shoots that will cover the cut areas. Pruning in late summer or fall is less ideal because the new growth stimulated by cutting may not harden off before winter, making those tender shoots vulnerable to cold damage and dieback.
Winter pruning is safe in the sense that the tree is dormant and you will not stimulate tender new growth, but the cuts will sit open and exposed for months before the tree can respond. In regions with heavy snow, there is also a practical concern: topped arborvitae with fresh flat cuts collect snow on the flat surface, and the weight can split the remaining branches apart.
How Much Can You Safely Remove at Once
A conservative guideline for arborvitae is to remove no more than about one-third of the tree’s total live foliage in a single year. For height reduction specifically, that usually translates to about one to two feet on a mature tree, assuming the tree is reasonably healthy and has decent foliage density near the cuts.
If you need to take off significantly more than that, a staged approach works better. In year one, remove a foot or so and also lightly prune the sides to encourage interior bud development. In year two, once the tree has pushed new growth near the previous cuts, take off another foot. This is slower, but the tree maintains enough foliage to stay healthy and the new growth fills in the gaps before you create more of them.
Trees that are already stressed, thinning, or have significant bare patches on the interior should be pruned even more conservatively. A struggling arborvitae that loses a third of its canopy may not have the energy reserves to recover, and you could end up with a dead tree instead of a shorter one.
Shearing Versus Selective Pruning
Many people maintain arborvitae hedges by shearing them with electric or manual hedge trimmers, taking a uniform pass across the top and sides each year. For a formal hedge that has been sheared regularly since it was young, this works well enough as ongoing maintenance because the dense outer shell of foliage stays intact. The trimmers only clip the newest growth, and the tree keeps its shape.
The problem comes when a sheared hedge has been neglected for several years and has grown well past its desired height. At that point, cutting it back to the old height means cutting through years of growth and into the bare interior. Shearing is a maintenance tool, not a corrective one. It keeps a tree at its current size; it cannot safely return a tree to a size it outgrew years ago.
If you have a hedge that has gotten away from you, the staged reduction approach described above is your best bet. Bring it down a foot or so per year while also lightly shearing the sides each spring to encourage the outer shell to stay dense. Over two or three seasons, you can reclaim a surprising amount of height without creating the bald, flat-topped look that gives topping its bad reputation.
Encouraging Density After Pruning
After reducing an arborvitae’s height, the tree will look a bit thin and uneven for a while. You can help it fill in faster by lightly shearing the outermost tips of the remaining foliage in late spring. This stimulates branching: instead of one shoot growing outward, the plant produces several shorter shoots from buds just behind the cut. Over a couple of seasons, this builds up a denser outer shell that hides the bare interior.
Fertilization can also help a pruned arborvitae recover. A balanced slow-release fertilizer applied in early spring gives the tree extra resources during its main growth period. Avoid heavy nitrogen applications in late summer or fall, which push soft growth that winter can damage. Consistent watering is just as important, especially in the first year after heavy pruning. Arborvitae are fairly drought-tolerant once established, but a tree recovering from significant foliage loss needs more water than usual to support new growth.
One thing that does not help is sealing the cuts with wound paint or pruning sealer. Research in arboriculture has consistently found that wound sealants do not prevent decay and can actually trap moisture against the cut, making fungal problems worse. A clean cut made with sharp tools heals best when left open to air.
Choosing the Right Variety to Avoid the Problem
If you have not planted yet and are trying to avoid a future topping situation, variety selection solves most of the problem before it starts. Arborvitae species and cultivars range enormously in mature height. Some of the most commonly sold varieties at garden centers are the tall ones, and buyers often underestimate how large they get.
Thuja occidentalis ‘Green Giant’ crosses with Thuja plicata genetics and routinely reaches 40 to 60 feet at maturity. Planting it as a privacy screen next to a single-story house is setting up a conflict that will eventually require either topping or removal. Thuja occidentalis ‘Emerald Green’ (also sold as ‘Smaragd’) tops out at roughly 12 to 15 feet, making it far more manageable for a residential privacy hedge. Dwarf varieties like ‘Hetz Midget’ or ‘Little Giant’ stay under four feet and are useful as foundation plantings where height is never the goal.
Matching the cultivar’s mature size to the space you have eliminates most future pruning headaches. Nursery tags sometimes list optimistic (small) mature sizes, so checking multiple references for a cultivar’s expected height in your climate zone is worth the few minutes it takes.
What About Cutting Back to a Stump
Some broadleaf trees and shrubs can be “rejuvenation pruned,” meaning you cut them nearly to the ground and they resprout vigorously. People sometimes wonder whether the same approach works for arborvitae that have become hopelessly overgrown. It does not. Arborvitae cut below all green foliage will almost certainly die. They do not have dormant buds along their trunks the way many hardwoods do, and without foliage to photosynthesize, they cannot fuel new growth.
If an arborvitae is so overgrown that a gradual reduction over multiple years still will not bring it to an acceptable size, the honest answer is that removal and replacement is the better option. A new tree of an appropriate cultivar, planted in the same spot, will look better within a few years than a severely topped and disfigured old tree ever will. This is not the answer most people want to hear when they are looking at a row of 30-foot arborvitae they need to shrink to 10 feet, but it is the reality of working with conifers.
Using Growth Regulators as an Alternative
Plant growth regulators (PGRs) are chemicals that slow a tree’s rate of elongation. Arborists sometimes use them on trees that need to be kept out of utility lines or kept below a certain height in commercial landscapes. They work by inhibiting the production of gibberellin, a hormone that drives shoot elongation. The tree stays healthy and green but grows at a fraction of its normal rate, buying several years before another pruning is needed.
For homeowners, PGRs are less commonly used because they typically need to be applied by a licensed arborist, they are not cheap, and they need to be reapplied every one to three years depending on the product. But if you have a row of arborvitae that you want to keep at their current height indefinitely without constant pruning, a growth regulator program combined with light annual shearing can be a practical approach. It will not make a tree shorter, but it can dramatically slow how fast the tree tries to get taller after you reduce it.
Repairing a Badly Topped Arborvitae
If you or a previous owner already topped an arborvitae and the tree now has the classic flat-top-with-bald-sides look, recovery is possible but slow. The first step is to select one of the uppermost shoots growing near the cut as a new leader. Stake it vertically if necessary by tying it loosely to a thin bamboo pole or wooden stake inserted into the top of the tree. Over a couple of years, this shoot will grow upward and begin to restore a natural pointed shape to the crown.
For the bald areas along the sides, patience is the main remedy. Lightly tip-prune any green growth near the bare zones to encourage branching toward the gaps. Some people tie neighboring branches slightly closer together to narrow the gap visually while waiting for new growth to fill in. In a healthy tree with good light exposure, noticeable improvement usually takes two to three growing seasons. In a shaded or stressed tree, it can take longer, and some gaps may never fully close.
If the tree was topped so severely that large sections have no green growth remaining, those sections are not coming back. At that point you are choosing between living with the appearance, planting a smaller shrub in front to screen the bare area, or replacing the tree. All three are legitimate choices depending on budget, timeline, and how much the appearance bothers you.