Britain has had its share of tree trouble over the years. Dutch elm disease wiped out millions of trees in the 1970s. More recently, sudden oak death has struck, and horse chestnut trees are currently suffering an outbreak of bleeding canker.

But experts say what makes most garden trees unsafe is not disease or nature taking its course, but human error.

Choosing an inappropriately large or fast-growing species for the space available in a modest garden is where many problems start. Eucalyptus, London planes and the famously antisocial leylandii are not suitable for smaller gardens, and homeowners soon realise that they have to be crowned, pruned or even felled.

That leads to the second most common problem, and the one that poses the most direct danger to the public, when amateur gardeners attempt to prune or crown the tree themselves.

“Incorrect pruning is a major problem. People tend to cut back far too hard, they cut incorrectly and the cuts don’t heal and decay sets in. Roots can even become diseased that way and the tree becomes unsafe. That is the case for all trees, regardless of the species,” Alan McWilliams, owner of Kent Tree Care, said.

“Alternatively, people start pruning their trees using just a ladder and lopping off the bits they can reach, when they really need climbing equipment to get to the top and prune it evenly. The tree then sprouts in an unbalanced way, with weak attachment points increasing the risk of falling branches. That is the real danger.”

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