HORSE CHESTNUT AVENUE
Tooting Common covers 92 hectares (221 acres) and is the largest open space in the borough. It has many diverse habitats, with its 3,300 trees forming a significant part of the landscape. The council has developed a comprehensive management and maintenance plan for the common, covering the next ten years.
The council is responsible for tens of thousands of trees, many of which require active management throughout their lifespans to ensure they remain safe and to tackle any health issues. Each year many trees require extensive pruning or even complete removal as their health and structural strength is affected by age, pests or conditions like fungal decay, bleeding cancer and ash die back.
These issues are common across the country, both within cities and rural settings. Examples of other locations to face significant tree management issues in recent years include Barrington Court (Somerset), Parkway Avenue (Hertfordshire), Wollaton Park (Nottingham) and Whaddon Recreation Ground (Cambridgeshire).
Chestnut Avenue runs northeast from the junction of Tooting Bec Road and Dr Johnson Avenue towards Bedford Hill, it is one of four historic avenues on the common. An ‘avenue’ is a double row of trees flanking a road, path or walk, and is planted with regularly- spaced trees of similar size and age, and to best effect, is of a single species. It is the uniformity of an avenue that makes it stand out as a landscape feature.
Chestnut Avenue was first recorded on Ordnance Survey maps in 1868, making it approximately 140-150 years old. The trees would normally grow for around ten years before being planted so the original trees themselves are likely to be between 150 and 160 years old. At this age chestnuts are approaching the end of their natural lifespan.
2015 Tree Surveys
To inform the Tooting Common management plan two tree surveys were commissioned in 2015:
1. Tree Condition Survey, by Treework Environment Practice: a general condition survey of all 3,300 trees on the common.
2. Heritage Tree Survey, by University of East Anglia: a more detailed survey focussed on the common’s trees with significant heritage value in terms of age, species and location, including the four historic avenues.
2015 Survey Findings Summary
Of the 77 trees in the avenue, 67 are horse chestnuts and both surveys indicated their condition is deteriorating due to a combination of age and other factors. Some have fallen over in the past, whilst others have required very significant pruning to remove weak limbs. These factors are causing the avenue to fragment and lose its value as a significant landscape feature.
The Heritage Tree Survey recorded 30 as being in ‘good’ condition with 43 described as ‘fair’ while two were ‘dead’ and two in serious decline. At that stage 20 trees were recorded as having contracted Bleeding Canker disease.
Due to various problems affecting the avenue as a whole and threats to the on-going viability of many of these trees, the Heritage Tree Survey’s authors concluded that “…serious consideration should be given to replanting of the avenue with another species.”
Tree Vitality and Structural Condition
In assessing tree condition there are two separate concepts to be considered – one is vitality which is the tree’s capability of growing new leaves, flowers and fruit, and the other is structural condition which is the trees capability standing intact, and not breaking. Trees being the organisms they are, the two are not particularly linked. Vitality is maintained by a healthy layer of active tissue, just under the bark. As long as this is intact, a tree is capable of transferring water and nutrients from the roots to the leaves and is capable of growing.
Structural integrity is dependent on the condition of the structural wood of the stem and branches. It is this latter condition that is of concern in Horse Chestnut Avenue. The trees contain many cavities, area of decay and other weaknesses. These do not affect the tree’s ability to grow but it means they are more prone to breakage and collapse.
Chestnut Avenue – Near Misses
The age and health conditions affecting the trees have led to several dangerous incidents. One tree fell over in February 2016 despite being judged in ‘fair’ condition in the 2015 tree condition survey.
Another two trees had to be urgently felled in 2017 after fungal brackets were identified which indicated serious internal decay and that they were structurally unsafe. The felled tree stems were left on site so people could see the extent of the internal decay.
Six other trees showed signs of decay and damage to the extent that extensive pruning had to be undertake urgently. During this work, one tree dropped a large branch revealing such serious internal decay that the tree had to be felled immediately.
The remaining large trees are in poor structural condition and will need increasingly severe pruning in the near future, and removals will be much more frequent. Because the avenue flanks a very busy footpath, tennis courts and children’s playground the risk posed by falling branches is far greater here than on other parts of the common.
2016 In-Depth Tree Condition Survey
Following the earlier survey results and safety incidents the council commissioned a more in-depth structural condition survey by Gifford Tree Services to inform this public consultation and next steps. This 2016 study focused only on the trees along Chestnut Avenue and involved a closer examination of each tree's structural condition.
2016 Survey Findings Summary
This survey indicated the avenue is in significantly worse condition than the earlier Heritage Tree Survey study suggested. Of the horse chestnut trees surveyed, one was the tree that had collapsed two more were recorded as dead , 26 were recorded as “poor”, 29 as “fair” and four as “good”. The difference between the surveys is attributed to the closer examination of the trees’ structural condition.
Read all the survey reports here.
Following the public consultation, the entire Horse Chestnut Avenue will be removed to allow for the re-establishment of a new avenue of trees of uniform species, age and size. Horse chestnut trees have only moderate lifespans in tree terms and they are not native to Britain. They are subject to a number of pests and diseases and they do not support as much biodiversity as other trees.
The removal of the existing trees will mean the new trees can grow unimpeded and will have all the light, water and air they need, and will therefore reach maturity more rapidly. This is the quickest way to establish a new avenue landscape feature for the common.
The trees used for replacement will be the small leafed lime. This species lives longer, is more durable, and by being a native British tree, will support greater biodiversity.
Works on site will be delivered in two phases. In the first phase all the trees and stumps will be removed and all surface roots will be grounded out to enable fresh tree pits to be excavated. The second phase will entail the delivery and planting operation of the replacement lime trees.