Is an hollow tree dangerous?

Homeowners naturally become concerned at any visible signs their tree is damaged. While a hollow tree might appear dramatic, it’s not always a cause for concern – in fact many hollow trees have stood and thrived for hundreds of years. However, Prince Tree would always advise you to seek the services of a professional tree surgeon who can make an expert judgement as to whether or not a tree is safe and healthy as the repercussions of ignoring the issue can be fatal.

Decay is part of the natural life cycle of many trees, particularly oak and ash. It takes many years or even decades for a tree to become hollow and although the heartwood (tree centre) is effectively dead, the tree will continue to form sapwood on the exterior of the trunk to create a cylinder. This cylinder can be extremely robust and will provide structural support to the trunk and the canopy above but it depends on the ratio of healthy to diseased tissue.

A hollow tree by itself is by no means an indication of weakness as many are strong and robust if there are no other problems or diseases affecting the tree. Many of the ancient trees we find in woodlands and parks are actually hollow and are perfectly healthy. It is usually younger trees which carry greater risk as they haven’t got the maturity to withstand significant decay and may become weakened as a result. A trained arboriculturalist will assess a tree in its entirety before determining whether it is safe or not.

There are of course times when a hollow tree is considered a danger and the only possible option is removal. Trees become unstable during the final stages of disease and may become more vulnerable to storm damage and high winds. This is when they pose the greatest risk to people and property and tree owners should take urgent action to ensure they minimise the chances of such events occurring.

Can I take action to correct a hollow tree?  

The simple answer is no. Trees which become hollow over time are often healthy and will create their own barriers of protection through the production of bark. A tree only requires the bark and the initial layers beneath the bark to remain strong and healthy. Filling in the hollow of a tree will not increase its stability, in actual fact it could do more harm than good, expanding and contracting at a different rate to the natural process. The general advice is to leave a tree untouched if shows no other signs of distress. Importantly, do not cause any damage to the outer layers of the tree as this will allow the rot to penetrate through to the essential layers.

Homeowners needs to ensure they gain the advice of an expert tree surgeon to determine the health of the tree initially and then follow this up with regular checks to ensure it is still structurally safe.