Common terms

Arboriculture: The science and art of caring for trees, shrubs and other woody plants in landscape settings.

Arborist: A person possessing the technical competence through experience and related training to provide for or supervise the management of trees or other woody plants in a landscape setting.

Biomass: The total mass, at a given time, of living organisms of one or more species per unit area (species biomass) or of all the species in the community (community biomass).

Bracing: Installation of steel rods or bolts through the stems or limbs, to reduce twisting or splitting of the wood.

Cabling: Installation of steel cables, attached to lag screws or bolts placed in tree limbs, to provide additional support or to limit movement and stress of limbs.

Cavity: An open and exposed area of wood, where the bark is missing and internal wood has been decayed and dissolved.

Compaction: The compression of soil, causing a reduction of pore space and an increase in the density of the soil. Tree roots cannot grow in compacted soil.

Conifer: Plant that bears seeds in a cone.

Core Sample: A sample of wood extracted from a trunk or branch, using an increment borer tool. The resulting core can be analyzed for characteristics of growth, structure, and decay, and for species identification.

Critical root zone: Portion of the root system that is the minimum necessary to maintain vitality or stability of the tree. Encroachment or damage to the critical root zone will put the tree at risk of failure.

Decay: Progressive deterioration of organic tissues, usually caused by fungal or bacterial organisms, resulting in loss of cell structure, strength, and function. In wood, the loss of structural strength.

Deciduous: Perennial plant that loses all its leaves at one time during the year.

Defoliation: Loss of leaves.

Dormant: Seasonal quiescent state in which the plant suspends growth. Usually occurs during winter months.

Evergreen: Plant that retains its leaves for more than one growing season.

Fertilization: The process of adding nutrients to a tree or plant; usually done by incorporating the nutrients into the soil, but sometimes by foliar application or injection directly into living tissues.

Foliage: The live leaves or needles of the tree; the plant part primarily responsible for photosynthesis.

Growth Increment: The incremental growth added as new wood each growing season over existing wood. This is seen as growth rings in cross-sections of wood.

Hardwood: Trees that lose their leaves in autumn; also refers to the wood produced by these trees. Hardwoods are the predominant type of tree in the deciduous forest.

Herbicide: A chemical that kills plants or inhibits their growth; intended for weed control.

Horticulture: Cultivation of fruits, vegetables and ornamental plants.

Insecticide: A chemical that kills insects.

Integrated Pest Management: System of controlling pests and their damaging effects through mechanical, chemical, biological, cultural and regulatory techniques.

Landscape: Areas of land that are distinguished by differences in landforms, vegetation, land use, and aesthetic characteristics.

Mitigation: Action taken to alleviate potential adverse effects on wetlands and fish habitat undergoing modification. Also commonly used to mean compensation for damage done.

Mulch: Any material such as wood chips, straw, sawdust, leaves, and stone that is spread on the surface of the soil to protect the soil and plant roots from the effects of raindrops, soil crusting, freezing, and evaporation.

Natural pruning: The natural death of branches on the stem of a tree from such causes as decay, or deficiency of light or water, or snow, ice and wind breakage.

Natural target pruning: Pruning technique in which only branch tissue is removed, with the cut placed just beyond the branch collar.

Nutrients: The substances, such as mineral elements and compounds, including water and air, that a plant synthesizes into the complex compounds of tissue.

Overmature: Tree or stand that has passed the age of maturity where the rate of growth has diminished and the trees are weakened.

Pruning: Selective removal of woody plant parts of any size, using saws, pruners, clippers, or other pruning tools.

Resistograph®: A gear-driven drilling instrument which inserts a three-millimeter-diameter probe into a tree, and graphically or digitally records resistance to the probe; used to detect decay and defects.

Root System: The portion of the tree containing the root organs, including buttress roots, transport roots, and fine absorbing roots; all underground parts of the tree.

Root Zone: The area and volume of soil around the tree in which roots are normally found. May extend to three or more times the branch spread of the tree, or several times the height of the tree.

Senescence: The process of aging, decline and death.

Softwood: Cone-bearing trees with needles or scale-like leaves; also refers to the wood produced by these trees. Softwoods are the predominant tree type in coniferous forests.

Soil: A dynamic natural body composed of mineral and organic materials and living forms in which plants grow.

Species: The main category of taxonomic classification into which living organisms are subdivided, comprising a group of similar individuals having a number of correlated characteristics.

Stress: Unfavorable deviation from normal. The action on a body of any system of balanced forces whereby strain or deformation results. In arboriculture, the adverse alteration of tree health by abiotic or biotic factors.

Target: Any person or object within reach of a falling tree or part of a tree, that may be injured or damaged.

Thinning: Pruning technique in which branches are removed at their point of origin.

Tree protection zone: A designated area around trees where maximum protection and preservation efforts are implemented to minimize soil compaction, etc.

Urban forestry: Management of naturally occurring and planted trees in urban areas

Vigor: Overall health; the capacity to grow and resist physiological stress.

Visual Tree Assessment: Method of evaluating structural defects and stability in trees.