Perenniporia fraxinea – managing risk (a case study)

Last year, I came across an ash (Fraxinus excelsior) tree that had a two-tiered bracket arrangement of Perenniporia fraxinea at its base. Given the ash was located right by a public footpath, and the fruiting bodies were on the compression side of the lean (wood is typically three times stronger under tension than compression), remedial works to reduce risk to a reasonable (ALARP – as low as reasonable possible) level were absolutely necessary.

Earlier this week, such remedial works were completed. The ash has been reduced significantly, though it still retains enough of a structure to enable it too look like a tree. Depending on how the ash fares (in terms of re-growth), there may be scope to eventually monolith it, in place of having it on what would need to be a cycle of maintenance every few years.

All of the material removed was piled at the base of the ash, as a sort of habitat pile. In time, as the wood decays, it may very likely be a good source for fungi and insects (particularly the larger pieces of wood, which easily are above 10cm in diameter). It also extends the hedgerow in a sense, by providing extra shelter from the adjacent open meadow.

Below are a few pictures from before and after.

Before being pruned, this ash had quite a large crown that stretches fully over the footpath. Here, we are looking at the ash from the tension side of the lean.

At its base, on the compression side, sit two Perenniporia fraxinea brackets. This photo was taken while standing on the footpath.

Following pruning works, the ash has had almost all of its branching structure removed. The wind sail area and overall weight of the tree has dramatically been reduced, and should hopefully reduce the risk associated with the ash’s presence. Beneath the tree, we can see one of wood piles created.

To give a sense of proximity to the footpath, I have included this photo. The path is rarely used during winter (it’s awfully sodden), though is slightly more frequently used during summer time.