Tree service glossary

Cleaning — per ISA, "removal of dead, dying, diseased, weakly attached, and low-vigor branches from the crown." This is the most commonly appropriate pruning for a mature tree. Raising — removing lower branches for clearance over walkways, drives and buildings. Thinning — reducing foliage density "to increase wind or light penetration." Reduction — reducing tree size, often for utility clearance, cutting back to secondary branches "at least one-third the diameter of the cut stem."

Topping — cutting limbs back to stubs to reduce height. Not a legitimate practice; ISA calls it "the most harmful tree pruning practice known," causing "unacceptable risk, tree stress, and decay." Crown — the branches and foliage above the trunk. Dieback — progressive death of branches from the tips inward, a decline symptom ISA associates with stress and root damage.

Codominant stems — two similarly sized trunks competing from the same point, a common structural weak point. Included bark — bark pinched inside a tight fork instead of wood, which prevents a strong union and makes failure more likely. Root flare — the widening where trunk meets roots; it should be visible above soil and mulch. Drip line — the ground area under the outer edge of the crown, a rough guide to root zone extent.

Cabling and bracing — hardware installed to support a weak union, covered by ANSI A300 supplemental support standards. Stump grinding — mechanically chewing a stump below grade, leaving roots to decay. Line clearance — pruning around energized utility conductors, work restricted to specifically qualified crews. Plant health care (PHC) — ISA's term for programs maintaining "appearance, vitality, and safety using the most cost-effective and environmentally sensitive practices."

How to choose

Make the quote name a pruning type

"Crown cleaning" and "crown reduction" are different jobs at different prices. "Trim" is not a specification.

Treat 'topping' as a disqualifier

Any company that offers it, or uses it as a synonym for pruning, is telling you what standard they work to.

Learn root flare and drip line

A buried root flare is a common and fixable problem. The drip line tells you what area to protect during construction.

Ask what defect the arborist term refers to

"Codominant with included bark at 12 feet" is a specific, checkable observation. Ask them to point at it.