Glossary For Tree Surgeons

Our glossary for tree surgeons here at Advanced Tree Services will help you to understand all the terminology that is associated with this comprehensive arboricultural service. If there is a term that you are unsure about that we haven’t included in the list below, please contact us for help.


Absorbing roots

These are roots that are fine and fibrous in design which take up both water and minerals from the ground.

Adaptive growth

This is when wood production is increased in localised areas as a response to a decline in external loading or wood strength. The result is that an even distribution of forces across the structure is maintained.

Adventitious growth

Also known as epicormic growth, this is when a new growth arises from dormant or new buds directly from main branches or stems, or even trunks.

Air spade

Making use of compressed air, this specialist excavation tool is used to remove and break up soil while causing minimal damage to roots and underground utilities.

Amenity value

This relates to the environmental and landscape benefits of trees, as opposed to their commercial value for timber.


This is the practice and study of the care of trees in the landscape.


Arborists are professionals who are able to provide for or supervise the management of trees in commercial, public and residential landscapes.


The debris that is caused from treeworks.


Barber chair

Leaning trees are at risk of suffering from this dangerous condition. This is because as the tree is cut, there is the chance that it will split vertically from the cut upwards with explosive force.

Bore cut

This is a technique for reducing the risk of the ‘barber chair’ condition occurring. This is because the method sees the tip of a saw plunged into a tree in order to form a hinge. When the saw is moved towards the back of the tree, a peg will be left that will stop the tree from falling until the hinge has been able to form correctly.


This is a knot that is used in order to form a secure loop in a rope. Items can then be attached.

BracingThis technique allows a weak area of a tree to be supported using cables, rods or straps, instead of this zone having to be removed.


Also known as brushwood, this is the collective term for branches and foliage removed from a tree up to approximately 150mm.


This is the British Standard Recommendations for Tree Work.


This is the British Standard Recommendations for Trees in Relation to Construction.

Buttress roots

These are the roots found at the base of a trunk.



These are cells that are found within many trees and plants. As these cells are meristematic (meaning that they can divide in order to produce new cells), they are able to produce both phloem cells and xylem cells.


This is when a hole is formed in a tree as a result of decay or damage.

Co-dominant stems

The name given to the process whereby two or more stems of around the same size and vigour are competing with each other for dominance.

Conservation area

This relates to a protection order whereby the Local Planning Authority (LPA) has to be informed ahead of any work to trees being carried out with a diameter over 75mm.


This is when the growth of a tree is entirely removed up to its stump so that the tree is able to re-generate. The traditional practice is only appropriate for certain ages and species of tree.

CordwoodThis is a type of timber that is more than 150mm in diameter, though smaller than around 300mm.

Coronet cut

Usually applied to trees found on wildlife sites, this is a finished cut that is applied to the tree in order to mimic natural tearing.


This is the part of a tree that is composed of branches and foliage.

Crown clean

This is the process of removing crossing, dead, dying, diseased and epicormic branches, as well as those which are causing a hazard.

Crown lifting

This is when lower branches are trimmed back, in order to enable top branches to rise as a result of weight loss.

Crown reduction

Also known as crown reshaping, this is when a tree is cut in order to trim and neaten it up.

Crown thinning

This is when congested roots are removed from a tree, to help light and wind pass through it better.



Due to safety concerns, this is wood that is often removed in order to create or maintain a feature tree. If suitable, it will be left on site in eco-piles for the sustainability of wildlife.


These are trees or plants that shed all of their leaves throughout the autumn months to prepare itself for winter.


This is a condition which indicates that the ends of a tree’s branches are dying.Dormant

This describes an inactive condition of a tree and is usually seen by deciduous trees during the coldest months of the year.

Drop crotching

This is the process of shortening a tree’s branches by pruning off the end back to a lateral branch which is at least 1/3 diameter of the removed branch.



This is a stacked pile of deadwood and arisings which have been removed from a tree, in order to help maintain and encourage wildlife.

Epicormic Growth

This describes the small shoots growing from the base of a tree. They can develop as a result of damage or stress to the tree, as well as being stimulated by pruning.


This is a tree that will continuously shed its leaves but will never shed all of its foliage.



This is the method for removing a tree by cutting at its base and then directing the entire tree to fall in a specific area.

Formative prune

This is the pruning of young trees in order to create a desired form or shape.


Also known as fruiting bodies, this refers to any spore-bearing structure which is found on a stalk of a tree or attached directly to it.


Growth rings

These are rings found in the xylem of the tree and also visible in a cross section of its stem, branch and, on occasion, the root.<h2>H</h2>


This relates to the shape of a tree.


This is where a dead branch has fallen from the crown of a tree but has been caught and is so resting on the branches lower down.

High hedge

This relates to hedges that have been deemed too high and so are causing a nuisance to the enjoyment of a neighbouring property.


ISA Certified Arborist

These are certified arborists who get their distinction by undergoing an examination and then need to keep up-to-date with the latest practices in their industry.

Included bark

This is bark that has been embedded within a tree, which causes a weakened structure.



This is the main upright stem or shoot found at the centre of a tree.


This is the process of removing branches from a tree in order to raise the height of the lower crown.

Lion tailing

This is a poor process of pruning whereby an excessive amount of branches is removed from inside the crown of the tree. As a result, clumps of foliage are left on the extremities of the limbs.


MatureThis is a tree which has attained its full size.


This is woody material which can be laid down over the rooting area of a plant in order to both reduce weed growth and retain moisture.


National Proficiency Tests Council

Also known by the acronym NPTC, this is the UK body responsible for providing proficiency tests for the use of chainsaws and forestry.



This is a pruning technique whereby the tree crown is cut back to bare branches on a regular occasion. It is a suitable technique only for certain species of tree.


This is when unwanted or damaged parts of a plant are cut away.


Reaction wood

This is wood which is formed on a weakened part of a tree.


This is the technique of reducing the height and sometimes the spread of a tree by cutting branches to laterals that are large enough to support a limb’s growth.

Remedial surgery

This is the treating or curing of a tree.


This relates to any timber which is larger than around 300mm (or one foot) in diameter.

Root crown

This is the area of a tree where the main roots join the stem.


Sail area

This is the area of a tree which is affected by the wind.


This is the outer part of a tree’s xylem which functions to transport water and minerals.

Scaffold branches

These relate to the main structural branches found within a tree’s crown.


This is the third phase of the life of a tree, following on from the youth and maturity stages. One of the main parts of this phase is the leaf area of a tree’s crown tending to diminish.


This is the supporting structure of a tree, which can be found from the ground level up to the first branch and works to transport food and water.

Stump grinding

This is the final stage of removing a stump permanently.



This is the removal of a small branch growth from throughout a tree’s crown. By doing so, air, light and wind penetration can be provided through the crown. The weight of the branches can also be lightened, all while maintaining the tree’s essential shape.


This refers to the pattern and structure of a tree’s branches.

Tree Preservation Order

Also known by the acronym TPO, this can be applied to any tree in order to protect it. As a result, work cannot be carried out on the tree without first gaining written consent from the local planning department.


Vascular system

This is the part of a tree that consists of the xylem and the phloem. The function of the system is to transport water and nutrients around the tree.


This relates to the life functions — both biochemical and physiological processes — of an individual, group or population of trees.



This refers to a group of branches that has arisen from the same level of a tree’s stem.


This is when the action of the wind causes the failure of an entire tree.


Woodchips are formed by processing branchwood through the use of a chipping machine. Once created, woodchips can be used to suppress weeds around an outdoor area.