As the holder of a large and valuable collection of trees, one of the best in the region, on a site to which some 200,000 visitors are welcomed annually, regular inspections of our tree stock are essential. Our in-house surveys have placed particular emphasis upon mature trees and those with known structural issues, while actions to reduce the risk have included the bracing of limbs and crown reductions. In order that we can better manage and record our tree collection, a comprehensive survey of all trees within the Garden was commissioned from Tim Moya Associates during the 2013 summer.
The survey provided us with vital information regarding the hazards and health condition of each of our trees and large shrubs which number around 2100 individual specimens. This information has been incorporated into our collections database (BGBase) and has resulted in a comprehensive programme of treework this autumn.
168 trees, representing 8% of the collection, were identified as requiring work; many need only the relocation of a bench sited beneath the canopy, the removal of ivy, minor dead wooding or branch reduction. In the majority of these cases, the highlighted work will have little impact on the appearance of the tree, and will enhance the health and life expectancy of the tree, while also minimising the risk. However, in a few cases, the required tree works will have a far greater impact, resulting in major reductions to the whole tree, removal of large limbs and in some cases in the removal of a mature, decaying specimen(s).
One such area requiring more substantial management was the stand of Caucasian wingnut, Pterocarya fraxinifolia, close to the Brookside Gate, whose imposing form is a significant feature of the Garden. The original planting of this tree numbers amongst the earliest plantings here in the Garden, and the multi-stemmed clump of mature suckers seen today is of great heritage value to us. As a mature specimen overhanging key access routes, work on these trees has been on-going for many years, and has included branch reductions and the removal of large trunks. The summer survey identified the need for further limb reductions and the removal of additional trunks. Elsewhere, some trees have been removed not only for the risk to public safety but for the risk posed to other trees of heritage value in the collection. The removal of the in decline Populus canadensis ‘Serotina’ in the Autumn Garden is a good example of this.
All the works highlighted by the summer survey were issued a works completion date; most works are required within 2 years. We expect to be undertaking tree work throughout the autumn and winter of 2013/2014, including stump grinding and spring replanting to ensure succession within the collection.
As the proud and professional custodians of an important tree collection, management such as this autumn tree work is well researched, well considered and guided by our responsibility to maintain and develop the collection into the future for research while making it safely accessible to the public. This work will support us in prolonging the life expectancy, wherever possible, of our mature tree specimens.