Arboricultural Association

The largest professional institution in the UK for the amenity tree care professional. Its purpose is to advance the study of arboriculture and promote the sustainable management of trees in areas where people live, work and play for the benefit of society.

Arboricultural Method Statement (AMS)

A plan that as part of the BS5837:2012 procedure defines how construction/site work should be carried out to avoid accidental damage to trees


The science and art of managing trees, shrubs and other woody plants for amenity

Asian longhorn beetle

The larvae of this native of China and southeast Asia feeds on broadleaved trees, weakening them by its boring activities.



Divided into three categories: Primary - a first order branch arising from a stem; Lateral - a second order branch, subordinate to a primary branch or stem and bearing sub-lateral branches; Sub-lateral - a third order branch, subordinate to a lateral or primary branch, or stem and usually bearing only twigs.

BS 5837:2012 Trees in Relation to Design, Demolition & Construction - Recommendations

The British Standard that sets out the arboricultural process that should be followed wherever trees or hedges are being considered in relation to development.


Chalara dieback of ash

A serious disease caused by a fungus (Hymenoscyphus fraxineus) which causes leaf loss and crown dieback. Usually fatal, it can kill a young tree in one growing season.

Construction Exclusion Zone (CEZ)

The root protection area from BS 5837 adapted for the actual development site to keep the required area around retained trees clear of any ground works, storage or potentially harmful activity. CEZs can include future landscape planting areas.

Crown reduction/shaping

A specified reduction in crown size whilst preserving, as far as possible, the natural tree shape.



Branch or stem wood bearing no live tissues. Retention of deadwood provides valuable habitat for a wide range of species and seldom represents a threat to the health of the tree. Removal of deadwood can result in the ingress of decay to otherwise sound tissues and climbing operations to access deadwood can cause significant damage to a tree. Removal of deadwood is generally recommended only where it represents an unacceptable level of hazard.


The death of parts of a woody plant, starting at shoot-tips or root-tips.


Environmental Impact Assessment (EIA)

A part of the planning process for identifying, predicting and evaluating the ecological and social impacts of a development proposal, together with suggested measures to minimize impact where appropriate.

Epicormic shoot

A shoot having developed from a dormant or adventitious bud and not having developed from a first year shoot.



A tree with densely formed, upright branches.

Feathered tree

A tree with balanced lateral shoots down to near ground level.



A form of artificial support with cables for trees with a temporarily inadequate anchorage.


Himalayan Balsam (Impatiens glandulifera)

Annual introduced to UK in 19th century. Classed as an invasive species, commonly found near waterways but now spreading along verges. Fast growing, it crowds out our native species.

Horse chestnut leaf miner

The potential weakening of horse chestnut trees caused by the caterpillars of the moth Cameraria ohridella 'mining' the leaves for food.



The establishment of a parasitic micro-organism in the tissues of a tree.

Institute of Chartered Foresters (ICF)

The Royal Chartered body for foresters and arboriculturists in the UK. It regulates the standards of entry to forestry and arboriculture and offers professional qualifications to promote expertise in the tree and woodland management professions.


Japanese knotweed (Fallopia japonica)

An invasive, non-native plant introduced to the UK by Victorian horticulturalists. It should be regarded as a form of contamination with implications for the natural and built environments.


Landscape Visual Impact Assessment (LVIA)

An assessment of the 'visual envelope' around a proposed development to identify implications for the immediate and wider landscape and suggest measures to mitigate any impact.


The hard constituent of wood cells.


A term often used to describe the removal of large branches from a tree, but also used to describe other forms of cutting.


Minor deadwood

Deadwood of a diameter less than 25mm and/or unlikely to cause significant harm or damage upon impact with a target beneath the tree.


Material laid down over the rooting area of a tree or other plant to help conserve moisture; a mulch may consist of organic matter or a sheet of artificial material - for example, a piece of old carpet.



A method of construction (usually paths) that does not involve any digging. Designed to get around working near trees where there is no alternative design option but suitable only for sites where ground levels do not need to be altered.


Oak processionary moth

This moth (Thaumetopoea processionea) is a native of central and southern Europe. Its caterpillars can rapidly defoliate a tree, forming long 'processions' along oaks to feed en masse. The hairs on the caterpillars carry a toxin that is harmful to humans and animals.



The removal of the tree canopy back to the stem or primary branches. Pollarding may involve the removal of the entire canopy in one operation, or may be phased over several years. The period of safe retention of trees having been pollarded varies with species and individuals. It is usually necessary to re-pollard on a regular basis, annually in the case of some species.

Public Open Space (POS)

Areas of open space included in a development in accordance with planning policy and agreed with the Local Planning Authority (LPA) as part of the planning negotiations or S.106 agreement.



The Quantified Tree Risk Assessment (QTRA) system applies proven risk management principles to tree safety management. Instead of focusing solely on a surveyor's descriptive assessment of a tree's condition, it takes into account its condition plus its value and risk to the site and the users of that site, then numerically quantifies the level of risk on an industry-accepted scale. This is particularly useful for those in charge of large tree stocks.


Root Protection Areas (RPAs)

The area around the base of a tree that contains sufficient root volume to ensure the future well-being of the tree in the event of nearby soil disturbance (as on a development site). It is calculated according to guidelines in BS 5837 (2012).

Royal Forestry Society (RFS)

An educational charity dedicated to promoting good management of trees and woods.



Living xylem tissues.

Section 106 Agreement

An agreement between developers and local planning authorities - usually involving Public Open Spaces (POS) - that is negotiated as part of a condition of planning consent whereby developers are obliged to contribute financially to general local amenity provision.


In woody plants, the normal abscission, rotting off or sloughing of leaves, floral parts, twigs, fine roots and bark scales.


In woody plants, a portion of a cut or broken stem, branch or root which extends beyond any growing-point or dormant bud; a snag usually tends to die back to the nearest growing point.


Target canker

A perennial canker, containing concentric rings of dead occluding tissues


In plant physiology, the movement of water and dissolved materials through the body of the plant.


The evaporation of moisture from the surface of a plant, especially via the stomata of leaves; it exerts a suction which draws water up from the roots and through the intervening xylem cells.

Tree Preservation Order (TPO)

TPOs are written orders administered by local planning authorities (usually the local council, or national park authority) that make it a criminal offence to wilfully damage or destroy (including prune or fell) a tree or area of trees deemed to offer 'significant amenity benefit'

Tree protection plan (TPP)

A plan showing the root protection areas of retained trees sufficient to allow them to thrive. It specifies the type of protection fencing required and gives details of any remedial tree or hedge work required.

Tree survey

Usually refers to the initial survey of trees on or near a potential development site, carried out in accordance with BS 5837. Commonly known as a BS 5837 survey, it marks the start of the arboricultural consultancy process.

Trees and Design Action Group (TDAG)

A national body set up to raise the profile of trees as a key part of infrastructure planning. Regional groups all over the UK provide information, guidance and coordination to make it easier for the relevant professionals and organisations to understand the issues involved.



A layer of vegetation beneath the main canopy of woodland or forest.



Water-conducting cells in plants, usually wide and long for hydraulic efficiency; generally not present in coniferous trees.



The blowing over of a tree at its roots.



One of the two types of transport tissue in vascular plants, phloem being the other. The basic function of xylem is to transport water from roots to shoots and leaves, but it also transports some nutrients.



A tropical Asian tree. Perfume is made from the flowers.

Yule log

A large log burnt in the hearth on Christmas Eve.