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."