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Fungal fruiting bodies like this are investigated with a visual inspection

Autumn's the time at Westonbirt when the Forestry Commission tree team carries out health and safety inspections on our collection. The team take into consideration the risk to visitors, staff, other trees and buildings from recognisable hazards such as decay or broken branches. Trees are not removed lightly, so the option to continue to manage trees in the collection is always explored if appropriate.

The arboretum is divided into three zones for inspection. Zone one contains high usage areas, near to paths and busy visitor areas, which are inspected annually each autumn. Zone two covers medium usage areas which are inspected every five years, and zone three contains low usage areas which have no formal inspection plan.

In addition to these different inspection zones, the team will look at around 100 trees for individual inspection each autumn. Trees on the list require special attention due to identified physical hazards including bracing or decay. Location is also considered if the tree is close to pathways or busy visitor areas.

A visual inspection is carried out. If required, technology is used to delve further into the problem.

Scanning the trunk to get a visual picture of the tree's health

Visual inspections involve investigating the type, position and size of fungus or pest on the tree. For example, some fungal fruiting bodies appear around the roots or buttresses whilst others appear on the trunk of the tree. The team also look at the tree's crown condition and search for any structural defects.

Often it's only the fungal fruiting body that can be identified visually, which means the tree team cannot necessarily see how far the pathogen has affected the tree internally.

If they want to investigate the problem more, they bring technology to scan the trunk to get a visual picture of the tree's health.

The picus sonic tomograph is just one example of equipment that's available and can be used in conjunction with other pieces of kit such as the resistograph. The uses sound waves to create a picture of how developed the decay has become. The resistograph drills into the tree to measure the wood's resistance, in effect measuring the depth of decay.

Many trees can continue to be managed and monitored in the tree collection for several years. However if a tree is deemed too hazardous and is seen to be a health and safety risk to visitors or other specimen trees, it will be removed.

This decision to remove a tree can often be an emotive one as the trees being felled are often old, original plantings. We always try to explain to our visitors why we remove trees; a process which in itself is highly skilled and carefully planned. Tree removal is important for the health and ongoing development of the tree collection as a whole.

The tomograph scan

One of the examples our tree team showed Autumnwatch was a mature beech (Fagus sylvatica) on Jackson Avenue in the Old Arboretum. It had been managed in the collection with a fungal fruiting body (Ganoderma species) on the trunk for several years. However, the tomograph and resistograph tests showed that there was significant decay and the decision was then taken to fell the tree.

When the tree team felled the beech, they found the cross section of the trunk showed a similar picture to that of the tomograph scan - confirming the value of using technology on these situations and that the tree had been felled for the correct reasons.

You can find out more about how the trees at Westonbirt Arboretum are managed, along with details about the wildlife and biodiversity of the arboretum on .