Reference

Tree care glossary

This tree care glossary defines 35 terms arborists and tree services use in quotes, permits and risk reports, from cabling and crown reduction to root plate and TRAQ, in plain English. Each definition stands on its own and links to the page that covers it in depth.

Last reviewed 2026-10-04.

Tree care terms: A

ANSI A300: The American national standard for tree care operations, covering pruning, support systems, risk assessment and other practices. Professional pruning specifications usually reference it. Tree trimming.
ANSI Z133: The American national safety standard for arboricultural operations, covering climbing, rigging, chainsaw use and work near electrical lines.
Arborist: A tree-care professional trained in the biology, pruning and safe removal of trees. An ISA Certified Arborist has passed the International Society of Arboriculture's exam and keeps up continuing education. How to hire a tree service.

Tree care terms: B

Bracing: Installing threaded steel rods through a weak union or split to reduce movement. It is often combined with cabling. Tree risk assessment.
Branch collar: The swollen area where a branch joins the trunk. Correct pruning cuts are made just outside it, so the tree can seal the wound. Trimming vs. pruning.

Tree care terms: C

Cabling: Installing flexible steel or synthetic cables between major limbs to limit how far they can move apart in wind. It reduces the risk of failure at a weak fork but does not fix decay or root problems. Can a leaning tree be saved?.
Co-dominant stems: Two trunks or leaders of similar size growing from the same point. The union between them is often weak, especially when bark is trapped inside it.
Conk: The shelf-like fruiting body of a wood-decay fungus on a trunk or root flare. A conk usually means significant internal decay. Signs a tree is dangerous.
Crane removal: Taking a tree down by cutting it into sections that a crane lifts away, used when a tree is too large, decayed or close to buildings to lower by rope. Large tree removal.
Critical root zone: The area around a tree, often estimated at 1 to 1.5 feet of radius per inch of trunk diameter, where root damage from digging or compaction most affects the tree's health and stability.
Crown: The branches and leaves of a tree above the trunk.
Crown reduction: Pruning that shortens the height or spread of a crown by cutting branches back to smaller lateral branches. Unlike topping, it keeps the tree's natural form.
Crown thinning: Selectively removing smaller live branches throughout the crown to reduce density and wind load, usually no more than about a quarter of the foliage at once.

Tree care terms: D

DBH (diameter at breast height): A tree's trunk diameter measured 4.5 feet above the ground. Many city tree ordinances use DBH or trunk circumference to decide which trees need a permit. Tree removal rules by city.
Deadwood: Dead branches in a tree's crown. Removing deadwood over roofs, drives and walkways is the most common safety pruning.
Defensible space: The area around a building where vegetation is managed to slow wildfire. Guidance usually focuses on the first 5 feet, then about 30 feet and 100 feet out. Preparing trees for wildfire.
Derecho: A long-lived, widespread windstorm from a line of thunderstorms, capable of hurricane-force gusts across hundreds of miles. Derechos cause large-scale tree damage in the Midwest and Mid-Atlantic. Storm damage tree removal.

Tree care terms: E

Emerald ash borer: An invasive beetle from Asia whose larvae kill ash trees by feeding under the bark. Infested ash usually die within a few years unless treated, and dead ash become brittle quickly. Dead tree removal.

Tree care terms: F

Felling: Cutting a tree down in one piece and dropping it in a planned direction, using a notch and back cut. It needs open space at least as long as the tree is tall.

Tree care terms: H

Hanger: A broken branch caught in the crown or resting on other branches. Hangers can fall without warning and are a common hazard after storms. Broken tree branches.
Hazard tree: A tree with a structural defect, such as a crack, decay, a failing root plate or a dead leader, positioned where its failure could hit people or property. Hazardous tree removal.
Heritage tree: A tree a city protects because of its size, age, species or history. Removing one usually needs a permit and is often allowed only if the tree is hazardous.

Tree care terms: I

Included bark: Bark trapped inside a narrow fork between two stems, which prevents the wood from joining and makes the union weak.

Tree care terms: L

Lion-tailing: Over-thinning a branch by stripping its interior growth and leaving foliage only at the ends. It shifts weight outward and makes branches more likely to break.

Tree care terms: O

Oak wilt: A fungal disease that kills oaks, especially red oaks and live oaks, spread by sap beetles to fresh wounds and through connected roots. In affected regions, oaks are not pruned during warm months and cuts are painted.

Tree care terms: R

Rigging: Using ropes, pulleys and friction devices to lower cut sections of a tree in a controlled way, instead of letting them fall onto roofs, fences or gardens. Tree removal.
Right-of-way tree: A tree on public land along a street, often in the strip between the sidewalk and curb. In many cities it belongs to the city, and residents need a permit to prune or remove it.
Root flare: The widening at the base of a trunk where it transitions into the main roots. A buried or damaged root flare can signal stability or health problems.
Root plate: The mass of soil and roots that anchors a tree. Soil heaving or cracking on one side of a leaning tree suggests the root plate is moving. Tree leaning toward house.

Tree care terms: S

Service drop: The overhead line running from the utility pole to a house. Utilities usually clear trees from primary lines, while homeowners are often responsible for trees near the service drop. Trees near power lines.
Stump grinding: Chipping a stump to below ground level, usually 6 to 12 inches, with a grinder. The roots stay in the ground and decay over time. Stump grinding.
Stump removal: Digging or pulling the stump and its main roots out of the ground. It leaves a larger hole than grinding and is used when a foundation or footing will go in the spot. Stump grinding vs. stump removal.

Tree care terms: T

Topping: Cutting a tree's main branches back to stubs to reduce its height. It is considered harmful because it causes decay and fast, weakly attached regrowth that breaks easily.
TRAQ: Tree Risk Assessment Qualification, an International Society of Arboriculture credential for arborists trained in a standardized tree risk assessment method. How tree risk assessments work.
Tree risk assessment: An arborist's evaluation of how likely a tree or part of it is to fail, what it would hit, and how serious the consequences would be, ending in a risk rating and recommendations. Tree risk assessment.

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