Is this tree safe? What the sources say about tree risk and who assesses it

This page reports what the official source says. It is not legal advice: ask the office named here. Nothing here is a view on any tree. The sources below say that judging the seriousness of a defect is work for a trained person who looks at the tree itself.

What ISA says about risk and owners

The International Society of Arboriculture (ISA) brochure on recognizing tree risk says there is "no such thing as a completely safe tree". It says all trees have the potential to fall but only a small number actually hit something or someone. It states that it is a tree owner's responsibility to ensure the safety of others around trees on their property, and that evaluating how serious a defect is "is best done by a professional arborist".

The brochure gives a tree risk checklist of questions an owner can ask when looking at a tree. They are whether there are:

large dead branches, detached or hanging branches, or branches that have fallen;
loose bark on the trunk;
cracks or splits in the trunk or where branches are attached;
an unusually developed trunk;
cavities or rotten wood along the trunk or in major branches;
mushrooms at the base of or under the tree;
recent changes to the area, such as construction, changes in soil level, or new lawns or pavement;
unusual yellow leaves, or leaves that seem smaller;
topping or heavy pruning in the tree's past.

It says an answer of yes to any of these, or any of the defects it shows, is a reason for the tree to be examined by an ISA Certified Arborist. The brochure also lists defect types in urban trees: poor taper, root failure, codominant stems, cankers and wounds, cracks and splits, external signs of decay, dead branches and human-caused defects. The site's guides on structural defects and cracks describe how arborists use those words.

What ISA says an arborist may suggest

The ISA managing hazards and risk page says an arborist familiar with tree risk assessment may suggest one or more of these: removing the target, such as moving a picnic table or car; pruning; cabling and bracing, which it says is not a guarantee against failure; routine care; or removing the tree. It says some trees with unacceptable levels of risk are best removed. The same page tells owners to find an arborist who holds the ISA Tree Risk Assessment Qualification.

What the qualification is

The ISA Tree Risk Assessment Qualification page describes TRAQ as a voluntary qualification. To earn it, a candidate completes a training course and passes a written and a performance-based assessment, and holders must retrain and retest every seven years. It says holders are trained in a standardized, systematic process for assessing tree risk and in giving information to tree owners and risk managers. The guide on tree risk assessment describes the methods, and becoming a consulting arborist lists the credentials in each country.

The United Kingdom view

The National Tree Safety Group says on its home page that it was formed in response to concerns about the unnecessary removal of trees from the UK's streets, parks and landscapes. It says its handbook, in a second edition dated 2024, sets out risk management guidance that it describes as common-sense and in proportion to the actual risks.

Where a tree has a Tree Preservation Order in England, the GOV.UK planning guidance on tree preservation orders and trees in conservation areas lists exceptions to the usual need for consent, including work on dead trees and branches and on dangerous trees and branches. It says the exception for dangerous trees applies where a tree presents an immediate risk of serious harm and work is urgently needed to remove it, and that written notice must be given to the authority as soon as practicable afterward. It says if the danger is not immediate, the tree does not come within the exception. The guidance is Crown copyright, licensed under the Open Government Licence v3.0, and this section is adapted from it.

At a glance

Source	What it says
ISA recognizing tree risk	No tree is completely safe; a professional arborist evaluates how serious a defect is
ISA managing hazards	An arborist may suggest moving the target, pruning, cabling, routine care or removal
ISA TRAQ	A voluntary qualification in a systematic risk assessment process, renewed every seven years
National Tree Safety Group	Risk guidance proportionate to the actual risks from trees
GOV.UK planning guidance	An immediate risk of serious harm is an exception to protected-tree consent

The guide on tree protection laws lists the permit offices by country.

Who to call

ISA Find an Arborist: finding and verifying individuals who hold an ISA credential, including the Tree Risk Assessment Qualification
Consulting arborists by country: the credentials and registers consulting arborists hold in each country
Tree protection offices: the city, county and council offices that handle protected-tree rules and permits
Working near power lines: branches or trees in contact with power lines: what regulators say about distances