Tree Surgery Terminology

Terms and Phrases Used in the Tree Surgery Industry

Tree Surgery Glossary

Welcome to the glossary section, where you can explore a comprehensive collection of terms related to the field of tree surgery, arboriculture and tree care. Whether you’re a tree surgeon, an arborist, a student, or simply someone with an interest in trees, this glossary is designed to expand your knowledge and understanding of key concepts, terminology, and practices within the world of tree surgery.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

The study and management of trees, shrubs, vines, and other woody plants.

Also known as a tree surgeon, a professional in the practice of arboriculture, responsible for the care and maintenance of trees.

Refers to non-living components in the environment that can affect tree health, such as sunlight, temperature, and soil quality.

The natural process by which trees shed their leaves, flowers, or fruit.

Soil with a pH lower than 7.0; certain trees prefer acidic soil while others do not.

Roots that form from non-root tissues like stems or older roots, often in response to stress or injury.

The process of increasing oxygen in soil, often to improve root health and nutrient absorption.

The chemical inhibition of one plant (or other organism) by another, due to the release into the environment of substances acting as germination or growth inhibitors.

A type of branching in trees where the branches and leaves grow alternately on the twig or branch.

A group of fungal diseases that affect a variety of plants causing dark, sunken lesions on leaves, stems, flowers, and fruits.

A document prepared by an arborist detailing findings about a particular tree or group of trees, often used for development planning or diagnosing tree health problems.

The angle or crotch formed by the branch of a tree and the stem or trunk from which it is growing.

Rings visible in a cross-section of a tree trunk representing one year of growth. They can be counted to determine the age of the tree.

The phenomenon where the main, central stem of the plant is dominant over other side stems; on a branch the main stem of the branch is further dominant.

The process of creating a new plant from the existing vegetative parts of a plant such as the stem, root, leaf, etc. This is often done in grafting.

B

A method of packaging nursery stock where the root ball is dug up and wrapped in burlap.

The protective outer covering of the trunk, branches, and roots of trees and other woody plants.

New growth that emerges at the base of a tree. Also known as a sucker.

A method of packaging nursery stock where soil is removed from the roots.

A plant that completes its life cycle in two years.

Refers to living components in the environment that can affect tree health, such as insects, fungi, and bacteria.

The main trunk of a tree.

The swollen area at the base of a branch where it is attached to the parent stem.

A ridge of bark that forms in the branch crotch (where the branch meets the trunk) and separates the dead wood of the branch from the dead wood of the trunk.

The installation of cables, ropes, or other materials to provide supplemental support to the tree structure.

A tree with leaves that are flat and thin, and generally shed annually.

An embryonic shoot that is the point of growth for new leaves, stems, or flowers.

Large roots on all sides of a tall or shallowly rooted tree, providing structural support.

A cutting tool used in pruning that makes a clean, close cut.

An area designed to separate different land uses to mitigate impacts or enhance compatibility.

A term for any of a wide range of symptoms that result in damage or death of plant tissues. Blights are often named after their causative agent, which could be bacterial, fungal or viral.

A type of grafting where a bud is attached to a rootstock to grow a new plant.

Materials that can be broken down by microorganisms (bacteria or fungi) into water, naturally occurring gases like carbon dioxide (CO2) and biomass.

C

A thin layer of tissue between the bark and wood that repeatedly subdivides to produce new growth.

The upper layer or habitat zone, formed by mature tree crowns and including other biological organisms (epiphytes, lianas, arboreal animals, etc.).

A necrotic (dead) area on the trunk, branches, or twigs of a tree, often caused by fungal or bacterial infections.

The green pigment in leaves that absorbs light energy for photosynthesis.

The yellowing of normally green leaves due to lack of chlorophyll, often caused by nutrient deficiencies or disease.

Sharp, spike-like devices worn on an arborist’s boots to aid in climbing trees. They should not be used on live trees that are being pruned, as they can damage the tree.

Two branches near the top of a tree that grow straight up and become equally dominant. This can create a weak spot in the tree, as these branches often push apart and split.

A type of tree that produces seeds in cones, such as pines, firs, and spruces. Most conifers are evergreen, but some (like larch) are not.

The branches, leaves, and reproductive structures extending from the trunk or main stems of a tree.

The selective removal of dead, diseased, and broken branches from the crown of a tree.

The removal of the lower branches of a tree to increase the distance between the base of the canopy and ground level.

The process of reducing the height or spread of a tree by selectively cutting back leaders to smaller branches.

The removal of selected branches within the crown of a tree to allow more light to pass through and reduce wind resistance.

A variety of a plant that was intentionally selected for particular attributes and maintained through cultivation.

A piece of a plant, usually a stem or leaf, that is used to grow a new plant.

Tissue formed over wounds in trees and other plants that prevent the loss of sap and protect against insects and diseases.

A traditional method of woodland management which exploits the capacity of many species of trees to put out new shoots from their stump or roots if cut down.

The fruiting body of a fungus that is typically found on tree trunks. Presence of a conk is often indicative of disease or decay.

The transfer of pollen from an anther of the flower of one tree to a stigma of the flower of another tree.

D

A fungal disease that kills or weakens seeds or seedlings before or after they germinate. It’s most common in wet and cool conditions.

Trees or shrubs that lose their leaves seasonally, most commonly during autumn.

The breakdown or rotting of wood due to fungi or other biological activity.

A tree form in which the branches arise from a common trunk, typical of most hardwoods. This growth habit is often seen in trees that have been regularly pruned.

 The scientific study of trees and woody plants, specifically their taxonomic classifications.

Condition in which a tree or shrub begins dying from the tip of its leaves or roots backwards, owing to disease or adverse environmental conditions.

The practice of planting trees by sowing seeds directly where they are to grow, as opposed to transplanting seedlings or saplings.

An imaginary boundary line on the ground surface that represents the outermost spread of the tree’s canopy. Rainwater generally drips from the tree canopy edge onto the ground along this line.

A period in an organism’s life cycle when growth, development, and physical activity are temporarily stopped, generally to conserve energy during harsh environmental conditions.

A deadly fungal disease of elm trees that is spread by elm bark beetles.

A tree significantly smaller than typical species size, often due to selective breeding or grafting.

A standard method of expressing the diameter of the trunk or stem of a standing tree. DBH is one of the most common dendrometric measurements.

The loss or shedding of leaves from a tree or other plant.

The process of cleaning tools to kill or inhibit the growth of disease-causing microorganisms.

A type of fruit in which an outer fleshy part surrounds a shell with a seed inside. Some trees, such as cherries, produce drupes.

Branches or parts of a tree that are dead and can often be a safety hazard if not removed.

E

A biological community of interacting organisms and their physical environment.

The removal of lower branches from a tree to provide clearance for buildings, vehicles, pedestrians, and vistas.

Trees that retain their leaves throughout the year. The leaves of evergreen trees are often needle-like in appearance.

 A term for a species that is native to, and restricted to, a certain geographic area.

A plant that grows harmlessly upon another plant and derives its moisture and nutrients from the air, rain, and sometimes from debris accumulating around it.

A tree or shrub that is trained to grow flat against a wall, fence, or trellis, often in a symmetrical pattern.

A plant that is not native to the region in which it is being grown.

The part of a branch that extends beyond the rest of the tree canopy.

A fluid, often sticky, that oozes from the trunk, branches, or leaves of a tree. This can be a sign of disease or injury.

The sum of evaporation and plant transpiration from the Earth’s land and ocean surface to the atmosphere.

A process in flowering plants grown in partial or complete absence of light, characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow colour (chlorosis).

A type of tree that has leaves that are broad, flat and thick, and remains green year-round.

The part of the tree’s annual growth ring that is formed early in the growing season when growth is rapid.

The process by which soil and rock are removed from the Earth’s surface by exogenetic processes such as wind or water flow, and then transported and deposited in other locations.

A species of organism that is at risk of becoming extinct due to a sudden rapid decrease in numbers or a severe reduction in its habitat.

F

The application of plant nutrients to support growth, typically involving elements like nitrogen, phosphorus, and potassium.

The plant life occurring in a particular region or time, generally the naturally occurring or indigenous plant life.

A pruning cut that goes into the trunk of the tree, removing the branch collar. This is usually harmful to the tree and is not a recommended practice.

The process of planning and implementing practices for the stewardship and use of forests and other wooded land to meet specific environmental, economic, and social objectives.

The leaf or leaf-like part of a palm, fern, or similar plant.

Vertical splits in the bark of a tree caused by rapid temperature changes in winter, typically on the south or southwest side of the tree.

A chemical compound used to kill or inhibit the growth of fungi.

A member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.

The science and craft of creating, managing, using, conserving, and repairing forests, woodlands, and associated resources to meet desired goals, needs, and values for human and environment benefits.

A term used to refer to a shrubby habit of growth.

A term used to describe the change in colour, curling and overall decline of an individual branch or entire sections of a tree, often due to disease, pest infestations or root issues.

A condition of plant growth in which the apical meristem (growing tip), which normally is concentrated around a single point and produces approximately cylindrical tissue, instead becomes elongated perpendicularly to the direction of growth, thus, producing flattened, ribbon-like, crested, or elaborately contorted tissue.

A contagious disease affecting apples, pears, and some other members of the family Rosaceae, which is characterized by wilting and blackening of blossoms and leaves, and is caused by a bacterium (Erwinia amylovora).

The leaves of a plant or tree, or leaves collectively.

G

The removal or damage of a ring of bark from around the entire circumference of a tree or branch. This can disrupt the flow of nutrients and water in the tree, leading to decline and possibly death.

This is a member of the tree surgery team who stays at ground level during operations. They are responsible for assisting the tree surgeon, removing debris, ensuring safety, and sometimes controlling traffic around the site.

A horticultural technique where tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together. This is commonly used in fruit tree propagation in the UK.

The act of removing a tree stump and its root system from the ground. This is often done to prevent the regrowth of the tree or to clear the area for other uses.

A protective device often used in tree surgery to prevent damage to the tree or to the tree surgeon. This might include climbing guards (to prevent damage to the tree) or chainsaw guards (to protect the operator).

These are the rings that you see when you cut a cross-section of a tree trunk. Each ring usually represents one year of growth, and the size of the ring can give you information about the conditions in that year (e.g., a wider ring usually indicates a good growth year with plenty of water and nutrients).

A group of seed-producing plants that includes conifers. The seeds of these plants are not enclosed within an ovary (contrary to angiosperms, or flowering plants). Many common trees in the UK, such as Scots Pine and Yew, are gymnosperms.

H

The natural home or environment of an animal, plant, or other organism.

This is a term used to describe wood from angiosperm trees, which are typically deciduous. This is opposed to softwood, which comes from gymnosperm trees, usually evergreens. In the UK, common hardwoods include oak, ash, and beech.

This is the innermost part of a tree trunk, which is typically denser and darker than the outer layers of wood (the sapwood). Heartwood is made up of old, dead wood cells and often contains compounds that make it more resistant to decay.

A row of closely planted shrubs or low-growing trees forming a boundary or fence. Hedges may require regular maintenance, such as trimming or pruning, to maintain a desired shape or height.

A tree surgery technique that reduces the overall height of a tree. This can be necessary for a variety of reasons, such as if a tree is interfering with power lines, posing a safety risk, or simply for aesthetic reasons.

A common disease in UK trees caused by the Armillaria fungus. It attacks and kills the roots of trees and can be a major problem, especially in managed woodland.

The science and art of cultivating plants, including trees. A tree surgeon needs to have a good understanding of horticulture to effectively care for trees.

A type of machinery used by tree surgeons to safely reach higher parts of trees. It consists of a platform at the end of a hydraulic system, which can be extended and retracted as needed.

I

Native to a certain area or region; not introduced.

A natural phenomenon in which trunks, branches or roots of two trees grow together. It’s most common in same-species trees where the bark has been removed or damaged, allowing the cambium layers to touch and fuse.

Refers to species that are not native to a specific location (an introduced species) and that have a tendency to spread to a degree believed to cause damage to the environment, human economy, or human health. In the context of UK tree surgery, examples might include the Japanese knotweed or the grey squirrel, both of which can pose significant challenges for the health and survival of native UK trees.

A type of climbing plant that often grows on trees. In the UK, English Ivy is a common species. While it can sometimes provide benefits, such as additional wildlife habitat, it can also be a problem if it overgrows and weakens a tree.

The invasion and multiplication of microorganisms such as bacteria, fungi, and viruses that are not normally present within a tree. Infections can cause a variety of diseases and health problems in trees.

The process of determining the species or type of a particular tree. This often involves examining characteristics such as the leaves, bark, flowers, or fruits of the tree. Tree surgeons need to be skilled at tree identification as different species can require different types of care and are susceptible to different pests and diseases.

A cut made into a tree, often as part of a tree surgery procedure. Incisions need to be made carefully to avoid unnecessary damage to the tree and to promote quick healing.

The portion of a plant stem between two nodes (where leaves or branches are attached). In tree surgery, understanding the structure of a tree, including aspects like the internodes, can be important for tasks like pruning or grafting.

J

A toxic compound found naturally in parts of the black walnut tree and some other plants. It inhibits growth of many plants.

In the context of tree surgery, joints often refer to the point at which a branch joins the trunk of a tree, or where smaller branches join larger ones. These joints, also known as nodes, are crucial points of interest when pruning or inspecting a tree for structural integrity.

A genus of trees, which in the UK is most commonly represented by the Walnut tree (Juglans regia). This is a hardwood tree species that can require specific care or management in terms of pruning and disease prevention.

A term used in the names of several species and varieties of plants from Japan that are cultivated in the UK. Examples include the ornamental cherries (Prunus × japonica) and the Japanese Quince (Chaenomeles japonica). These plants may require care from tree surgeons for correct pruning or disease management.

A type of tool used in tree surgery. This tool has a bypass blade design for more cutting power at the pivot and is used for cutting branches that are too high to reach with standard loppers.

A type of coniferous plant in the cypress family. Some species are native to the UK, and junipers can require specific care in terms of pruning and disease management.

The early growth phase of a tree, during which it often grows rapidly. In this phase, trees can require specific care, including formative pruning to encourage good structure as they mature.

K

A hard, woody imperfection in a tree where a branch used to be; a cross section reveals it as a circular or oval shape.

The wood that makes up a knot, which is usually harder and has a different grain pattern than the surrounding wood. Knotwood is often visible in sawn timber and can affect its properties and uses.

While not native to the UK, Kauri dieback is a disease caused by a water mold that affects Kauri trees. It’s included here as tree surgeons in the UK may work in other countries or need to be aware of international tree diseases for study or biosecurity reasons.

In the context of trees, a “knee” often refers to a distinctive structure found in some species, such as the Bald Cypress, where roots protrude above the ground in a knee-like formation. Although not common in UK native trees, tree surgeons may encounter them in parks or gardens with a variety of tree species.

A type of hardwood that is dense and strong. It’s not a UK native, but may be encountered in the context of imported timber or exotic trees grown in gardens.

A common type of weed in the UK. While not directly related to tree surgery, tree surgeons need to understand the wider ecosystem in which trees grow, which can include knowledge of common weeds.

L

A bud located on the side of a stem that has the potential to grow into a branch, flower, or leaf.

The primary vertical stem of a tree. Trees typically have one leader (known as excurrent growth habit), but can sometimes have multiple leaders (known as decurrent growth habit).

Branches that grow out to the side of the tree, as opposed to the leader, which grows upwards. Lateral branches contribute to the overall shape and stability of the tree.

A large primary branch of a tree. The term is often used interchangeably with “branch,” although it generally refers to larger branches.

An older term for the practice of cutting branches or tops off trees. This term has generally been replaced by the term “pruning,” as lopping can sometimes imply less careful or more severe cutting.

A symptom of stress in a tree, where the edges of the leaves turn brown and crispy. It can be caused by a variety of factors, including drought, salt exposure, and certain diseases.

A type of organism that is a symbiotic partnership of a fungus with an algae or bacterium. They often grow on the bark of trees and are usually harmless, although a large amount of lichen could indicate that the tree is not in good health.

A term for a length of the trunk of a tree after it has been felled and the branches removed.

The process of cutting down trees, usually for timber or to clear land. This term is more commonly used in forestry rather than tree surgery.

M

A layer of material applied to the surface of soil to conserve moisture, improve soil health, reduce weed growth, and enhance visual appeal of the area.

A tree that has reached its full growth or size. Mature trees often require different care compared to young or middle-aged trees.

A symbiotic association between a fungus and the roots of a plant. In this relationship, the fungus helps the tree absorb water and nutrients from the soil, while the tree provides the fungus with sugars.

A type of flowering plant that typically has one seed leaf, or cotyledon. Monocots include grasses and lilies, but not many trees, with palms being a notable exception.

A small, soft plant that grows close together in damp or shady locations. While often harmless, moss growing on a tree can sometimes indicate that the tree is not in the best health.

Damage to a tree caused by mechanical means, such as from a lawnmower, a car, or improper pruning. This can harm the tree and make it more susceptible to diseases and pests.

A type of parasitic plant that grows on the branches of trees and shrubs. In the UK, mistletoe most commonly grows on apple, lime, and poplar trees.

The regular care of trees to ensure their health and safety. This can include activities such as watering, fertilizing, pruning, and disease and pest management.

N

The part on a plant stem where a leaf or a bud is attached.

A condition in which a tree is lacking one or more of the essential nutrients needed for healthy growth. Symptoms can include discolored or malformed leaves. Nutrient deficiencies can often be corrected with appropriate fertilization.

A species that naturally occurs in a particular region. In the UK, native tree species include the English oak, Scots pine, and silver birch. Tree surgeons often work with native species and need to understand their specific care requirements.

The death of plant tissue, often resulting in browning or blackening. Necrosis can be caused by a variety of factors, including disease, physical damage, or environmental stressors.

The process by which trees regrow naturally from seeds or sprouts after a disturbance, such as a fire or a logging operation. Natural regeneration can play an important role in forest management and restoration.

The process by which nitrogen is converted between its various chemical forms in the environment. Nitrogen is an essential nutrient for trees, and understanding the nitrogen cycle can be important for managing soil health and tree nutrition.

A place where young trees (often called seedlings or saplings) are grown until they are large enough to be transplanted to their final location. Some tree surgeons may work closely with nurseries to source trees for planting.

O

The layer of foliage in a forest canopy. It includes the crowns of the tallest trees.

A branch or part of a tree that extends out over a road, a building, or another area. Overhangs can sometimes pose a risk and may need to be pruned for safety reasons.

A common type of tree in the UK, known for their strength and longevity. There are several species of oak in the UK, including the English oak and the sessile oak.

A tree that is grown primarily for its aesthetic appeal, rather than for timber or other uses. Ornamental trees can require specific care to maintain their appearance and health.

Trees, like all green plants, produce oxygen as a byproduct of photosynthesis. While this isn’t a term specific to tree surgery, understanding the role of trees in the ecosystem, including oxygen production, is an important part of arboriculture.

Material derived from the decay of plants and animals. In soil, organic matter contributes to fertility and water-holding capacity, both of which can affect tree health.

Extensions on some types of equipment, such as cranes or lifts, that provide stability when the equipment is in use. Tree surgeons may use machinery with outriggers when working on large trees or in difficult-to-reach areas.

P

The process by which green plants and some other organisms use sunlight to synthesize foods with the aid of chlorophyll. This process involves the conversion of carbon dioxide and water into glucose, releasing oxygen as a by-product.

A method of pruning that involves cutting back the tree branches to the trunk, promoting a dense head of foliage and branches. Pollarding is mainly done for safety reasons or aesthetic purposes.

A branch that emerges directly from the trunk of the tree.

The selective removal of certain parts of a plant, such as branches, buds, or roots. In tree surgery, this is often done to remove deadwood, shaping a tree, improving or maintaining health, reducing risk from falling branches, preparing nursery specimens for transplanting, and both harvesting and increasing the yield of flowers and fruit.

The scientific study of plant diseases. Tree surgeons need to have a basic understanding of this to identify and treat tree diseases effectively.

The vascular tissue in plants that transports nutrients and carbohydrates, produced by photosynthesis, from leaves to the rest of the tree.

A bacterium, virus, or other microorganism that can cause disease. Tree surgeons often encounter various pathogens that can cause tree diseases.

Gear that tree surgeons wear to protect themselves from potential hazards during tree surgery operations. This can include helmets, eye protection, hearing protection, gloves, safety boots, and chainsaw protective clothing.

The process of creating new plants from a variety of sources such as seeds, cuttings, and other plant parts. Tree surgeons might propagate trees for replanting in certain areas.

Trees that have a lifecycle lasting more than two years. Unlike annuals or biennials, perennials tend to grow and bloom over the spring and summer, die back every autumn and winter, and then return in the spring from their rootstock.

Organisms that can cause harm to trees, such as insects, fungi, and other pests. Tree surgeons need to identify and manage pests to maintain the health of the trees they are caring for.

A legal instrument in the UK that prohibits and/or restricts the movement of certain plants, trees, and related materials (including fruit and wood) which can carry pests and diseases.

A part of UK law which is made by a local planning authority (LPA) to protect specific trees, groups of trees or woodlands in the interests of amenity. An order prohibits the cutting down, topping, lopping, uprooting, wilful damage, or wilful destruction of trees without the local planning authority’s written consent.

Q

The Latin name for the oak tree genus, which contains about 600 species of trees and shrubs. Some common species include Quercus rubra (red oak), Quercus alba (white oak), and Quercus robur (English oak).

A hedge created by planting live hawthorn cuttings directly into the earth. Also known as a living hedge, it can require careful maintenance and pruning.

A restriction on the movement of plants and plant products to prevent the spread of pests and diseases. Tree surgeons in the UK must comply with quarantine regulations set out by the Department for Environment, Food and Rural Affairs (DEFRA)

A pattern of planting trees or shrubs where each plant in the four corners of a square, and a fifth one in its centre, essentially forming a grid. This may be used in certain landscaping or reforestation efforts.

In the context of tree surgery, this refers to a method of pruning wherein the canopy of a tree is reduced by a quarter to decrease the sail effect of wind and reduce the risk of storm damage.

These are animals that eat tertiary consumers, often carnivorous and located at the top of the food chain. The health of trees can indirectly affect these creatures by impacting the overall ecosystem health.

R

The part of a plant that typically lies below the surface of the soil, absorbs water and nutrients, and anchors the plant.

The expansion of a tree in diameter, usually measured in the growth rings visible in a cross-section of the trunk. This growth is often assessed by tree surgeons to determine tree health.

The process of replanting or regrowing forest areas that have been cut down or otherwise damaged. Tree surgeons can play a key role in reforestation efforts by planting and caring for young trees.

The area of a tree where the trunk transitions into the root system. This area should generally be left exposed for tree health.

The process of cutting back a tree’s roots to encourage new growth and to help contain the size of the tree. This is often performed on trees being prepared for transplantation.

A horticulture term used to describe the base part of a grafted or budded plant. The rootstock is selected primarily for its interaction with the soil, while the upper part, or scion, is chosen for its fruit, flowers, or leaves.

The region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil health in the rhizosphere can impact tree health.

An evaluation of potential hazards and the severity of harm that could be caused. In tree surgery, this includes evaluating the potential risk of falling branches, disease spread, etc.

The mass of roots and soil attached to a plant’s base that is removed from the ground when the plant is uprooted for transplantation.

Also known as girdling, it is the removal or peeling of a ring of bark from a tree. This action can cause the death of the tree, as it disrupts the flow of nutrients and water from the roots to the leaves.

A sticky substance secreted by some trees, particularly conifers, when they are wounded. Some pathogens can be deterred by the tree’s resin.

The interface between land and a river or stream. Trees in these areas often require specific care due to their importance in maintaining water quality and preventing erosion.

The decay of tree material due to fungi. Tree surgeons should be able to identify and treat various types of rot to preserve tree health.

A UK-based educational charity dedicated to promoting the management of trees and woods to meet the needs of the environment and society.

In the UK context, it can refer to Tree Preservation Orders (TPOs), Conservation Areas, Felling Licences or other rules and regulations that tree surgeons need to be aware of when undertaking work.

S

The younger, outermost wood of a tree that is involved in the transport of water and nutrients from the roots to the rest of the tree.

A branch that emerges from a primary branch. This term is often used when discussing the structure and pruning needs of a tree.

In horticulture, this term refers to a tree form in which a single stem or trunk is encouraged to grow tall, with the branches and canopy starting at the top of this trunk.

The process of removing a tree stump by using a machine to grind it down into chips. This is often done after a tree has been felled to improve aesthetics and remove a tripping hazard.

The part of a tree’s trunk, branches, and roots that lies between the heartwood and the bark. It is newer, softer wood that transports water and nutrients throughout the tree.

The process of applying pressure to the soil, which increases its density and decreases its porosity. Soil compaction can be harmful to tree health by reducing the availability of oxygen to tree roots.

The practice of controlling the planting, growth, composition, health, and quality of forests to meet diverse needs and values. While not a part of tree surgery per se, knowledge of silviculture is valuable for tree surgeons, especially in larger woodland contexts.

The part of the tree where growth takes place, usually towards the tip of branches. It includes both the stem and leaves.

A form of protective equipment used by tree surgeons when working at height. It secures the worker to the tree and can prevent falls.

A process of treating seeds to simulate natural conditions that a seed must endure before germination. In tree planting, stratification can be used to improve seed germination rates.

A basal shoot rising from the base of a tree or its roots. Suckers can drain energy from the tree and are often removed.

A basic unit of biological classification and a taxonomic rank. Tree surgeons must be familiar with different tree species, their specific characteristics, and requirements.

A tool consisting of a tough blade, wire, or chain with a hard toothed edge. It is used to cut through material, most commonly wood. Types used in tree surgery include hand saws, chainsaws, and pole saws.

The collection of data for the purpose of analysis and future management decisions. A tree survey can include information on a tree’s species, height, trunk diameter, crown spread, health condition, and management recommendations.

The interaction between two different organisms living in close physical association, typically to the advantage of both. Many trees have symbiotic relationships with fungi and other organisms.

The main structural part of a tree from which leaves and flowers grow. Also known as the trunk of the tree.

Primary limbs that form the tree’s canopy. Proper selection of scaffold branches early in a tree’s life can minimize potential issues such as weak crotches and can help to reduce the need for more drastic pruning later in the tree’s life.

A facility where logs are cut into lumber. While tree surgeons don’t usually operate sawmills, the wood from removed trees often ends up at these facilities.

T

A perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species.

The process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapour and is released to the atmosphere.

A type of pruning that selectively removes branches to increase light penetration and air movement through the crown of a tree.

The main structural part of a tree, from which the branches grow.

A controversial practice that involves cutting back the branches of a tree to stubs or to the trunk to reduce the tree’s size.

A person, often employed by a local authority, who is responsible for maintaining, planting, and protecting trees within their jurisdiction.

The process of moving a tree from one location to another.

The process of cutting down a tree.

A hole dug in preparation for planting a tree. It should be broad and shallow with a firm base to support the tree.

A support placed in the ground for a tree to help it stay upright, usually used when the tree is young or newly transplanted.

The practice of managing trees, shrubs and other woody plants by arborists or tree surgeons.

The bud located at the end of a stem or branch. It’s primarily responsible for allowing the stem to grow longer.

The wood of trees cut and prepared for use as building material.

Branches that grow from secondary branches. They’re the smaller branches that give the tree’s crown its overall shape.

The degree to which a substance can harm a tree or other living things. Tree surgeons need to understand potential toxin sources, including certain tree treatments and environmental contaminants.

Stress that a tree can experience after being transplanted from one place to another. This can lead to the tree wilting, losing leaves, or even dying.

The classification of trees based on their age, which can help determine appropriate management strategies.

A document outlining how a group of trees, forest, or urban tree population will be managed, with goals such as maintaining tree health and safety.

U

The vegetation layer of plants and small trees growing beneath the main canopy of a forest.

In the context of tree surgery, this term can refer to the measures taken to support or strengthen trees, such as bracing or cabling.

The care and management of tree populations in urban settings for the purpose of improving the urban environment. An urban forester, or tree surgeon, may deal with a range of issues from pest management to planting for maximum energy conservation.

The action of pulling a tree out of the ground by its roots, often due to strong winds or ground movement. Tree surgeons may need to deal with uprooted trees, particularly following storms or other extreme weather events.

The management of trees near utility lines. This can involve specific pruning techniques to ensure that trees do not interfere with power lines and other infrastructure.

Another term for rootstock or the root part of a grafted plant.

The government’s approach to sustainable forest management. It outlines standards and requirements for the diverse range of benefits that forests provide.

The practice of planting smaller plants and trees beneath larger ones. This can create a layered effect and helps to use all available space within a planting area.

V

This term refers to the system of tissues in trees that transport water, nutrients, and sugars between the roots and the leaves. It consists of the xylem (which carries water and nutrients upward from the roots) and the phloem (which carries sugars, a product of photosynthesis, from the leaves to the rest of the tree).

Thin sheets of wood of uniform thickness sliced or peeled from a log. This term is more relevant to wood processing but is included as tree surgeons need to understand the value of the trees they handle.

A term used to describe trees that are of interest biologically, culturally, or aesthetically because of their age. They are typically old, with a combination of size, age, damage, or other unique features that signify their significance.

The practice of pruning trees to enhance a particular view. This is often done in parks or gardens where trees might obstruct scenic views.

In the context of tree surgery, vitality refers to the physiological health or “fitness” of the tree. A tree with high vitality has a strong capacity for growth and resistance to disease or damage.

The abnormal development of green pigmentation in plant tissues normally not green, such as flowers or fruit. It can be a sign of viral infection.

A term used to describe a plant that grows on its own, rather than being deliberately planted by a human. This term is used frequently in discussions about tree management, as volunteer seedlings can become problematic if they are not properly managed.

A technique used to reduce soil compaction in the root zones of trees. It involves drilling holes in the soil and filling them with nutrient-rich material.

A disease that attacks the vascular system of a tree, often leading to wilting, decline, and eventual death of the tree. One of the common types affecting trees in the UK is Dutch Elm disease.

W

Vigorous vertical growth coming off the branches or trunk of a tree. These shoots are usually removed during pruning as they can drain energy from the tree and disrupt its structure.

A UK-based charity that aims to protect the country’s woodland and promote the planting of trees.

Refers to trees uprooted or broken by the wind. It’s a natural process, especially in extreme weather conditions, but can also be a result of improper management practices.

A pattern of branches where several branches form at the same point on the trunk or a branch, creating a “whorl” or circle around the trunk.

Fungi that digest and break down the wood in trees. Some wood decay fungi can cause significant damage to trees and even result in their death.

A piece of equipment used in tree surgery to reduce tree limbs or trunks into smaller chips.

New stems that grow from the trunk of a tree, usually as a response to stress, pruning or damage. They’re often seen as undesirable because they grow rapidly and can alter the shape of the tree or weaken its overall structure.

The presence of bark or lack of wood from the corners of a piece of timber, which indicates that the timber came from the outer sections of the log.

The wood that forms in response to a wound, often creating a swollen area around the site of injury. This wood helps to seal off the wound and protect the tree from disease and infestation.

Legislation that provides protection for animal species, including their habitats, and restricts the introduction of certain non-native species. It’s important for tree surgeons to be familiar with this Act to ensure their practices don’t harm protected wildlife or contravene the regulations.

Land covered with trees, usually larger than a grove or a copse but smaller than a forest. The management of woodland requires a broad knowledge of arboriculture and forestry.

X

The vascular tissue in plants that conducts water and dissolved nutrients upward from the root and also helps to form the woody element in the stem.

A form of gardening that focuses on plants with low water needs, to conserve water. While not a term exclusive to tree surgery, knowledge of xeriscaping can be useful when selecting or recommending tree species in drought-prone areas or environments where water conservation is important.

A plant that is adapted to survive in an environment with little water, such as a desert or an ice-covered region. Some trees fall into this category.

Also known as Cherry X-Disease, it’s a harmful disease affecting certain types of trees, particularly cherry trees. It’s spread by leafhoppers and can cause serious damage.

A yellow or brown carotenoid pigment which causes the autumnal yellow colour of deciduous leaves. As with other terms related to leaf pigments, it helps in understanding tree physiology and responses to changes in the environment.

Y

Trees that are located in a yard or residential area, as opposed to a forest or orchard.

A type of tree native to the UK, often found in churchyards and can live for over a thousand years. The common yew (Taxus baccata) is a highly toxic plant that can be harmful or even fatal to humans and animals if ingested.

In the context of trees, yellowing often refers to chlorosis, or the yellowing of tree leaves due to lack of chlorophyll. This can be caused by a number of factors, including nutrient deficiencies, poor drainage, or disease.

A tree that is relatively early in its life cycle. These trees often require special care to ensure their healthy growth and development.

In forestry and tree management, yield refers to the amount of usable wood a tree or area of woodland produces.

Refers to green waste such as grass or flower cuttings and hedge trimmings, as well as domestic or industrial waste.

In forestry, yarding is the process of moving logs from the stump to a landing area. This is not a common activity for a tree surgeon but is part of the wider logging and forestry industry.

Z

The highest point in the sky directly above the observer. In arboriculture, it might refer to the very top of the tree.

Refers to the tree’s natural defence mechanism against the spread of disease or decay. When a tree is wounded, it can isolate the affected area to prevent disease or decay from spreading to the rest of the tree. This process is formally known as Compartmentalisation of Decay in Trees (CODIT).

This term generally refers to an animal that resembles a plant in appearance or lifestyle, such as certain types of coral or sea anemones. In the context of tree surgery, it might be used to describe tree pests that are sessile or plant-like in their behaviour.

An essential micronutrient for plants. Deficiency in zinc can lead to various symptoms in trees, including reduced leaf size, shortened internodes, and leaf chlorosis.

The cell resulting from the fusion of male and female gametes. In the context of tree reproduction, this would refer to the fertilised cell that eventually develops into a seed.

Sometimes called “spalted wood,” zone lines are barriers constructed by a tree in reaction to decay fungi. These lines are often darkly pigmented and may be used as a decorative feature in woodworking.

A type of leaf disease that creates distinct rings or zones of damage on the leaves. This disease can affect a variety of trees and may be treated with various fungicides or by improving the overall health and vitality of the tree.