As Tree Surgeons and Arborists, we use some interesting terms to describe trees, their structure, growth processes and the work we do.  Here is a selection of the most commonly used Tree Surgery terms, but if you have any others you would like to know more about, please don’t hesitate to contact us below.

Tree Surgery in West Sussex

Adaptive Growth

Areas of wood production in a tree increase because of a decrease in wood strength or external loads to maintain even distribution in the overall structure.

Adventitious/Epicormic Growth

New growth arising from dormant or new buds directly from main branches/stems or trunks.

Co-dominant Stems

Two or more, generally upright, stems of roughly equal size and strength, growing at a similar rate and competing with each other for dominance. Where these grow from a common union the structural integrity of that union should be assessed.


The cutting down of a tree within 300mm (12in) of the ground at regular intervals, traditionally applied to certain species such as Hazel and Sweet Chestnut to provide stakes etc.


The foliage bearing section of the tree formed by its branches and not any clear stem/trunk.

Crown Reduction

The reduction in height and/or spread of the foliage bearing portions of a tree. Crown reduction may be used to reduce mechanical stress on individual branches or the whole tree, make the tree more suited to its immediate environment or to reduce the effects of shading and light loss, etc. The final result should retain the main framework of the crown, and a significant proportion of the leaf bearing structure.  The process should leave a similar although smaller outline, and not necessarily achieve symmetry for its own sake. Crown reduction cuts should be as small as possible and in general not exceed 100mm diameter unless there is an overriding need to do so. Not all species are suitable for this treatment and crown reduction should not be confused with ‘topping’ which is an indiscriminate and harmful treatment.


The application of a nutritional substance, usually to the tree’s rooting area (and occasionally to the tree), to promote tree growth or reverse or reduce decline. This will only be effective if nutrient deficiency is confirmed. If decline is the result of other factors such as compaction, physical damage, toxins etc., the application of fertiliser will not make any difference.

Formative Pruning

Careful pruning during the early years of a tree’s growth to establish the desired form and/or to correct defects or weaknesses that may affect growth or structure in later life.

Fungi/Fruiting Bodies

Plants that may grown on living or dead tissues of a tree or form beneficial relationships with the roots. The fruiting body is the spore bearing, reproductive part of a fungus. Removal of the fruiting body will not prevent further colonisation and will make diagnosis treatment harder to determine. Each colonisation must be considered in detail by a competent person to determine the long term implications of tree health when considered alongside the tree species and environmental factors.


Bracing is describes the use of cables, ropes and/or belts to reduce the probability of failure of one or more parts of a trees structure.  Usually due to weakened elements experiencing excessive movement.

Branch Bark Ridge and Collar

Natural features of a fork or union that may or may not be visually obvious. Neither the branch bark ridge nor collar should be cut.

Crown Thin

Usually used for broad-leaved trees, crown thinning is the removal of some smaller/tertiary branches, usually at the outer crown, to produce a uniform density of foliage around an evenly spaced branch structure. Crown thinning does not alter the overall size or shape of the tree. Material is removed systematically throughout the tree, should not exceed more than 30% overall. Common reasons for crown thinning are to allow more light to pass through the tree, reduce wind resistance, reduce weight and is rarely a once-only operation particularly on species that are known to produce large amounts of epicormic growth.


Dead branches or stems due to natural ageing or external influences. Deadwood provides essential habitats and its management should aim to leave as much as possible, shortening or removing only those that present a risk. Durability and retention of deadwood will vary by tree species.


When a tree shows signs of a lack of vitality such as reduced leaf size, colour or density.


Tips of branches exhibit no signs of life due to age or external influences. Decline may progress, stabilise or reverse as the tree adapts to its new situation.

Lopping and Topping

Generally regarded as outdated terminology but still included as part of Planning legislation. Lopping means the removal of large side branches (the making of vertical cuts) and topping refers to the removal of large portions of the crown of the tree (the making of horizontal cuts, generally through the main stems). Often used to describe rough, heavy-handed or inappropriate pruning.

Painting or Sealing

Covering pruning cuts or other wounds with a paint, often bitumen based. Research has demonstrated that this is not beneficial and may in fact be harmful. On no account should treatments for timber be used as these are harmful to living cells.


Pollarding is the initial removal of the top of a young tree at a prescribed height.  This is done to encourage multi-stem branching from that point, traditionally for fodder, firewood or poles. Once started, it should be repeated on a regular, cyclical basis always retaining the initial pollard point, or bolling as it is known.


Growth of a tree as a result of wounding and which become specialised tissues of the repair over time.


A void within the solid structure of the tree, normally caused by decay or deterioration of the woody tissues. These can be dry or can contained water.  Water holding cavities in trees should not be drained. Only any soft, decomposing tissue should be removed if necessary. No attempt should be made to cut or expose living tissue.

Crown Lift or Crown Raising

Crown lifting is the removal of the lowest branches, it can also include preparation of lower branches for future removal. Crown lifting should not normally include the removal of large branches growing directly from the trunk as this can cause large wounds. Large wounds can become extensively decayed leading to further long term problems or more short term biomechanical instability. Crown lifting on older, mature trees should be avoided or limited to secondary branches or shortening of primary branches rather than the whole removal. Crown lifting is an effective method of increasing light transmission to areas closer to the tree or to enable access under the crown but should only be less than 15% of the live crown height and leave the crown at least two thirds of the total height of the tree.


The inactive tree, usually during the coldest months of the year when there is little or no growth and leaves of deciduous trees have fallen.

Drop Crotching

Shortening branches by pruning off the end back to a lateral branch which is at least 1/3 of the diameter of the removed branch.

Retrenchment Pruning

A type of tree or shrub reduction intended to encourage development of lower shoots and emulate the natural process of tree ageing.

Root Pruning

The pruning of roots (similar to the pruning back of branches). This can affect tree stability so it is advisable to seek professional advice prior to attempting.


The degree of life functions – both physiological and biochemical processes within a single, group or population of trees.

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