Tree Service Terms Glossary

Welcome to our comprehensive Tree Service and Arborist Glossary, designed to provide clear and concise definitions of common terms used in the tree care industry. Whether you're a seasoned arborist, a tree service professional, or a homeowner looking to understand more about proper tree maintenance, this glossary offers valuable insights into the terminology essential for tree care. From pruning techniques and tree biology to specialized equipment and legal protections, our goal is to help you better understand the practices that keep trees healthy and landscapes thriving.

Abatement: The process of reducing or eliminating a tree hazard through pruning, treatment, or removal of targets like structures.

Adaptive Growth: The increased production of wood in specific areas of a tree to compensate for structural weaknesses.

Adventitious Root: Roots that emerge from unusual places, such as tree stems or branches, often triggered by stress or injury.

Adventitious/Epicormic Growth: Shoots that emerge from dormant or new buds, typically in response to stress or pruning.

Adventitious Shoot: New growth that forms from areas of a tree that don't normally sprout, often as a response to pruning or damage.

Allelopathy: A natural phenomenon where a plant releases chemicals to inhibit the growth of nearby plants.

Amendment (Soil): A material added to soil to improve its physical properties, such as aeration, drainage, or nutrient content.

ANSI A300: A standard created by the American National Standards Institute that provides best practices for pruning and maintaining trees.

Antagonism: When two chemicals, such as pesticides, produce a weaker effect together than if used separately.

Apical Control: The dominance of the central leader (main trunk) over lateral branches, common in conical trees.

Appropriate Lateral (Lateral Pruning): Pruning that involves cutting branches back to a lateral limb to maintain natural growth patterns.

Arboriculture: The practice and science of cultivating, maintaining, and caring for trees, especially in urban or landscape settings.

Arborist: A trained professional who specializes in the care, management, and health of trees, often performing tasks like pruning, planting, and diagnosis.

Basal Flare: The outward swelling at the base of a tree where the trunk meets the roots, providing stability.

Best Management Practices (BMPs): Guidelines or standards that represent the most effective methods for managing and caring for trees based on current knowledge.

Bleeding: The oozing of sap or fluid from a tree wound, often following pruning or injury.

Bole: The main trunk of a tree, extending from the base to the first significant branch.

Bow: A gradual bend in a tree branch or trunk, often caused by growth patterns or external forces.

Bracket (Fungus): The fruiting body of wood-decay fungi, often visible on the outer surface of the tree.

Bracing: The installation of cables or rods to provide structural support to weakened or damaged branches.

Branch: A secondary shoot growing out from the main trunk of the tree.

Branch Angle: The angle at which a branch attaches to the trunk, influencing its strength and potential for breakage.

Branch Collar: The swollen area at the base of a branch where it connects to the trunk, critical for making proper pruning cuts.

Branch Protection Zone: A small area at the base of a branch that helps resist decay and discoloration following injury.

Caliper: A measurement of a tree's trunk diameter, typically used to size nursery trees.

Canopy: The upper layer of a tree, made up of branches and foliage.

Cavity: A hollow or decayed section within a tree, often formed by rot or damage.

Central Leader: The primary upward-growing stem that dominates the tree’s structure in species like conifers.

Circling Roots: Roots that grow in a circular pattern around the tree, often restricting growth and stability.

Clay Loam: A type of soil with a balance of sand, silt, and clay, often used for landscaping and tree planting.

Cleaning: The removal of dead, dying, or diseased branches from a tree's crown.

Codominant Leader: When two or more stems of similar size compete for dominance, creating a weak structural point.

Compartmentalization: A tree's natural process of isolating damaged or decayed tissue from healthy tissue.

Compression Wood: A form of reaction wood that forms on the underside of branches and leaning trunks in conifers.

Conservation Area: A protected area designed to conserve wildlife and vegetation, requiring permission for tree work.

Crown: The section of the tree made up of branches, leaves, and foliage.

Crown Clean: The removal of dead, dying, or hazardous branches from a tree to improve safety and aesthetics.

Crown Lift: The removal of lower branches to raise the canopy height, providing clearance for structures or light.

Crown Reduction: Reducing the size of a tree’s canopy by cutting back its branches to improve shape and reduce stress.

Crown Thin: Selective removal of branches within the crown to reduce its density, allowing for better air flow and light penetration.

Deadwood: Non-living branches within the tree, often removed to reduce safety hazards.

Deciduous: A type of tree that sheds its leaves annually, usually in the fall.

Decurrent Tree: A tree with a broad, spreading crown and no dominant central leader, typical of species like oaks.

Drop Crotching: A pruning technique that shortens branches by cutting them back to a lateral branch.

Evergreen: A tree or shrub that retains its foliage year-round, such as most conifers.

Excurrent Tree: A tree that grows with a single, straight trunk and conical form, such as pines and redwoods.

Felling: The process of cutting down a tree by sawing it at its base, often directing its fall to a specific area.

Field Capacity (FC): The amount of water a soil can hold after excess water has drained away.

Fibrous Root System: A root system composed of many small roots that spread out horizontally rather than developing a single deep root.

Flush Cut: A pruning cut made too close to the trunk, removing the branch collar and impairing the tree’s ability to heal.

Formative Pruning: Early-stage pruning designed to shape young trees and encourage strong, healthy branch structure.

Fungi: Organisms, such as mushrooms, that break down dead wood but can also infect living trees.

Girdling Roots: Roots that grow around the trunk, restricting its growth and cutting off water and nutrient flow.

Included Bark: Bark that grows between two branches or stems in a narrow, weak "V" shape, creating a risk of splitting.

Live Crown Ratio: The proportion of a tree’s total height that is occupied by live foliage.

Loam: A balanced soil type ideal for plant growth, containing a mix of sand, silt, and clay.

Lowest Permanent Branch: The lowest large branch that will remain part of the tree's structure long-term.

Macronutrient: Essential nutrients required in large amounts for plant growth, such as nitrogen and phosphorus.

Meristem: Tissue in plants capable of dividing and generating new growth, found in the tips of roots and shoots.

Mulch: A protective layer of material spread on the soil surface to retain moisture and improve soil quality.

Pollarding: A pruning method where the upper branches of a young tree are cut back to promote dense, multi-stemmed regrowth.

Proper Cut: A pruning cut made just outside the branch collar to allow for natural healing and minimize decay.

Radial Trenching: A method of soil aeration around a tree by creating radial trenches, often filled with organic matter.

Reaction Wood: Wood that forms in response to stress, helping the tree maintain structural integrity.

Reduction Cut: Pruning that reduces the size of a branch by cutting back to a lateral branch that can assume the terminal role.

Resistograph: A diagnostic tool used to measure the density of wood and detect decay inside a tree.

Retrenchment Pruning: A method of reducing the size of a mature tree to encourage new growth at lower levels.

Root Collar (or Root Flare): The transition area between the trunk and roots, where the trunk begins to spread out at ground level.

Root Pruning: Cutting back tree roots to encourage growth, often performed with care to avoid destabilizing the tree.

Sapwood: The outer, living part of a tree's wood that transports water and nutrients.

Scaffold Branch: One of the major limbs that form the basic structure of the tree's crown.

Scion: A young shoot or twig used in grafting to propagate a tree with desired characteristics.

Sucker Growth (or Water Sprouts): Vigorous vertical shoots that emerge from the tree's roots or lower trunk, often due to stress or damage.

Subordinate Pruning: Pruning smaller branches to allow larger, more important branches to thrive.

Target: Any person or property that could be harmed in the event of tree failure.

Temporary Branch: A branch that serves a temporary purpose but will eventually be removed to improve the tree's structure.

Tension Wood: A form of reaction wood in angiosperms, forming on the upper side of a branch or leaning stem.

Thinning Cut: A pruning cut that removes a branch at its point of origin or back to a lateral branch.

Topping: The harmful practice of cutting back the main stems or large branches, often leading to decay and poor regrowth.

Tree Preservation Orders (TPO): Legal protections placed on specific trees, requiring permission from authorities before they can be pruned, removed, or altered.

Vigor: The overall health and energy of a tree, influencing its ability to grow and resist stress.

Vitality: A measure of a tree’s overall health, including its ability to grow and resist stress.

Weight Reduction Cut: Removing portions of a branch to reduce the load on a weak or heavy limb.

Wetwood: Wood with a higher moisture content, resistant to decay but prone to bacterial infections.

Woundwood: New tissue that forms over wounds in trees as part of the healing process.

Xylem: The tissue in trees that transports water from the roots to the leaves.