A dangerous tree is one that is likely to cause serious damage to property or injury to people. Many trees become unstable when entering the latter stages of disease – though perfectly healthy, young trees can also become a danger if damaged by severe weather.
How to Spot a Dangerous Tree
- Look closely at the ground around the tree trunk for a clear indication of any problems. If, on a windy day, you can spot signs of ground movement (‘heave’) or cracking, there may be cause for concern. Look for raised soil opposite to the tree's natural lean, which could indicate uprooting.
- If a tree is overhanging a road or building, don’t hesitate in seeking the advice of a professional tree surgeon or arboriculturist. Most commonly the tree will not have to be removed in its entirety – just the limbs causing the potential danger.
- Fungal growth like mushrooms on or near a tree trunk is indicative of rot or decay. To determine if the tree is unsafe, you need to know how extensive the decay is. Call a certified arborist or tree surgeon if you see fungal growth around the base of a tree.
- Look for places on the tree’s trunk where there is no bark. This can indicate a dead section or a fungus attack.
- Sometimes a tree grows two or more trunks. The points where the multiple trunks connect must be inspected for weakness or past storm damage. Stronger connections appear as a U shape at the crotch. A tight V shape usually evidences a weak connection.
- One of the most obvious tree dangers is dead wood that can fall. You can spot dead wood easily: dead branches have leaves that are completely brown or there won't be any leaves at all.
Is a tall tree dangerous?
No. A tree will grow (within its species limits) as large as the space, light, water, nutrition and oxygen available to it permits. Trees cannot grow too tall - except in human perception.
Is a leaning tree dangerous?
Not necessarily. One of the reasons a tree grows with a lean is because it is in close competition with another specimen and has been forced to grow at an angle to chase the light. In response the tree lays down denser wood on one side of its trunk. There may be a problem however if a previously vertical tree suddenly develops a lean.
Is a hollow tree dangerous?
Certainly some hollow trees may have so little healthy tissue surrounding the hollow area that they must be regarded as dangerous, but this is by no means the norm. Trees do not become hollow overnight - it can take decades - and while the centre of the tree (the heartwood) may be decaying, the tree continues to lay down healthy wood (sapwood) around the outside of its trunk. This results in the formation of a cylinder, the strength of which depends upon the percentage of healthy to unhealthy tissue.
TPOs and Dangerous Trees
Some trees are protected by TPOs - Tree Preservation Orders. These trees are normally highly visible to the public, and integral to the local environment. Should you wish to work on - or remove - a protected tree, you will need to seek permission from your local council.
If the tree constitutes an immediate risk, you can take steps to make the tree safe prior to receiving permission - but the onus is on you to prove that the work was absolutely necessary.
If you identify a dangerous tree owned by somebody other than yourself, express your concern to them and encourage them to take action. If the tree is deemed ‘imminently dangerous’, the council can require the owner to act by law.
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