Why Tree Topping Harms Trees, and What to Ask For Instead

What exactly counts as topping?

The International Society of Arboriculture (ISA) defines topping as the indiscriminate cutting of tree branches to stubs, or to side branches too small to take over as the new end of the limb. You may also hear it called heading, tipping, hat-racking or rounding over. The key word is indiscriminate. The cut is made at a chosen height, not at a point where the tree can respond to it.

That is the difference between topping and legitimate size reduction. One uses cuts placed where the tree can seal them and keep a natural form. The other ignores the tree's structure. ISA calls topping perhaps the most harmful tree pruning practice known.

Why does topping hurt the tree?

It starts with food. Leaves and needles are where a tree makes its energy, and ISA notes that topping can remove 50 to 100 percent of a tree's leaf-bearing crown. The tree responds by forcing out a flush of new shoots below each cut to replace the lost foliage as fast as it can. If it does not have the stored reserves to do that, ISA says, it will be seriously weakened and may die.

The wounds are the second problem. A proper pruning cut is made just outside the branch collar, where a healthy tree is equipped to close the wound. A topping cut made between branches leaves a stub the tree may not be able to close. The exposed wood begins to decay, and ISA observes that few trees can defend the multiple severe wounds topping causes. Bark that grew up shaded is also suddenly in full sun, which can lead to sunburn beneath the bark, cankers, splitting and the death of some branches.

Finally, ISA notes that a stressed tree with large open wounds is more vulnerable to insect and disease infestations.

What happens in the years after a tree is topped?

The tree grows back, quickly and badly. The shoots that erupt below each cut are not built like normal branches. ISA explains that a normal branch develops in a socket of overlapping wood, while these shoots are anchored only in the outermost layers of the parent limb. They can grow fast, as much as 20 feet in a single year in some species according to ISA, so the height you paid to remove returns within a few seasons, carried on weak attachments above a decaying stub.

That is why ISA states that the risk of limb failure after topping has increased, not decreased, especially in windy or icy conditions. Washington State University Extension makes the same point about maintenance: a topped tree needs repeated, costly work to keep the regrowth in check. ISA adds that a topped tree can never fully regain its natural form, that topped trees are considered an impending expense where healthy trees add to property value, and that because topping is regarded as an unacceptable practice, damage from a failed limb on a topped tree may lead to a finding of negligence. That last point is general information, not legal advice; an attorney or your insurer is the right source for your situation.

Why is topping especially bad for Montana conifers?

Most of the big trees on western Montana lots are conifers: ponderosa pine, Douglas-fir, spruce, larch. They grow from a single leader at the top. Washington State University Extension describes what happens when that leader is cut: the tree keeps growing from several points instead of one, and the exposed top may rot, with branches loosening as the rot spreads.

Purdue University Extension explains the mechanism in a pyramidal evergreen such as a spruce. The growing tip suppresses side growth, which is what gives the tree its pointed form, and Purdue notes that this form helps the tree shed heavy snow. Remove the tip and the tree grows rounder, with multiple competing tips, and is exposed to splitting down the trunk. Purdue's conclusion is blunt: large evergreens do not respond well to topping, and topping to control size is not justified.

Doesn't a shorter tree at least catch less wind and snow?

For a season or two, perhaps. After that, the answer reverses. The regrowth is dense, fast and weakly attached, which is the worst combination to load with the heavy, wet snow that western Montana gets in spring and fall. A topped conifer with several competing leaders has several unions where one sound stem used to be. If wind and snow are the worry, the goal is a tree with good structure and less end weight, which is a pruning question. Our guide to winter tree care and snow load looks at which trees are most at risk.

What should you ask for instead of topping?

Ask for reduction, and ask how the cuts will be made. ISA describes the method: small branches are removed back to their point of origin, and a larger limb that must be shortened is cut back to a side branch at least one-third the diameter of the limb being removed, large enough to take over as the new end. Done this way, the tree keeps its natural form and the wounds are ones it can close.

There are limits. ISA's general guidance is that no more than about 25 percent of the crown should come off at once, and less for a mature tree. Washington State University Extension also notes that crown reduction suits trees with a rounded shape and does not work for pyramidal conifers. So a maple or a cottonwood can often be reduced; a spruce or a fir generally cannot be made shorter and stay healthy. Most reduction is best scheduled as dormant pruning.

How do you open a view or let wind through without topping?

This is where conifers have good options. Washington State University Extension describes three, all of which rely on the fact that a branch stays at the height where it grew. Skirting, or limbing up, removes branches from the ground to a chosen level so you can see under the crown; the extension suggests not going higher than half the visible height of the tree. Interlimbing, or thinning, removes selected branches along the trunk for a filtered view and more light, and the extension notes it leaves less mass for wind to push against. Windowing removes branches from one section of the trunk to frame a view.

Limbing up is also part of defensible space on wildland-urban interface lots, so a view project and fire mitigation work can often be planned together. Where the conflict is with overhead wires, the utility has its own clearance pruning, covered in our guide to who trims trees near power lines.

When is removal and replacement the honest answer?

When the tree is simply the wrong size for the place it was planted. ISA says it plainly: sometimes the best solution is to remove the tree and replace it with a species more appropriate for the site. Purdue gives the same advice for evergreens that have outgrown their space. A large-growing spruce set a few feet from a house, or a tall tree directly under a power line, will be a problem for as long as it stands. Our list of the best trees to plant in western Montana includes small trees suited to tight spots.

What if the tree has already been topped?

It is worth having it looked at instead of assuming the worst. ISA notes that a topped tree that survives will likely need corrective pruning within a few years, and its tree risk checklist asks directly whether a tree has been topped or heavily pruned, because of the weak regrowth and decay that follow.

HJ Property Care does not top trees. Pruning is done to ANSI A300 and ISA practice, which is set out on our tree services page, and a tree health and risk assessment will tell you whether a previously topped tree can be managed or should come out. More guides like this one are collected in the Montana Tree Guide.

Call HJ Property Care & Tree Service at (406) 215-7319 or request a tree assessment and an ISA Certified Arborist will look at the tree with you.

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