When is a tree not a tree?

Laurence Gale & Peter Britton in Conservation & Ecology

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That is a question that could be asked of the Royal Oak, perhaps the most famous tree in the world and one that countless public houses in England are named after

The Royal Oak sits within the grounds of Boscobel House, a timber framed hunting lodge in Shropshire, now under the stewardship of English Heritage. It was the then-owner, John Giffard of Whiteladies, who famously hid the fleeing King Charles II in the branches of the tree after a heavy defeat at Worcester in, what turned out to be, the final conflict of the Civil War in September 1651.

In truth, the tree is 'daughter of Royal Oak' as the original was plundered and eventually killed by souvenir hunters. It is the last and younger remaining of two trees that seeded within the protective wall of the site; its older sibling suffering a similar fate to the original.

Charles II was eventually responsible for the Restoration of the Monarchy in 1658, following almost a decade of rule by 'Lord Protector' Oliver Cromwell. It was the King's popularity with his people that saw the Royal Oak given such legendary status.

Whilst there is plenty more to write about Charles II's 'colourful' reign, it is the preservation of the tree - now considered to be at least 250 years old - that is of interest.

The tree stands in a field currently laid to pasture which, until recently, had been arable. It is protected by iron railings, installed in 1817 (which replaced the original protective wall), with further more recent additional fencing to keep visitors safely away from its rooting area.

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With English Heritage concerned for the tree's health and also the safety of visitors, the organisation sought the services of Chartered Arboriculturist, Neville Fay, Principal Consultant at Treework Environmental Practice and hugely experienced in veteran trees.

Neville first inspected the Royal Oak in early 2011, and was commissioned to assess its viability following a significant storm in September 2010 which caused serious structural damage. The tree had been previously struck by lightning during the summer of 2001, with severe consequences, causing a substantial section of the crown to tear away and fall. The lightning strike damaged the upper trunk and led to the death of the south facing side of the main stem, causing the root system on this aspect to atrophy.

The 2010 storm resulted in additional damage to an already vulnerable trunk and crown, raising concern for the risk of further breakage. The tree had been subject to post-storm emergency remedial tree surgery, including circumferential-bracing of the hollow trunk. Given the tree's recent history of losing parts of the crown, in addition to structural concerns regarding further collapse, there were also concerns that additional wounding and loss of foliar cover would compromise the longevity of the Royal Oak.

Neville explains: "My appraisal considered the tree from the point of view of its structural and physiological condition, with a view to exploring restorative and conservation options. The initial inspection considered whether the residual crown was sufficient to sustain the tree during its recovery phase following the recent damage, and the prospects for the mechanical state of the trunk and the crown framework."

"In this context, options were considered to reduce the risks of further failure in the short term and the potential in the longer term to enhance the tree's mechanical and physiological condition."

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"A key issue was, therefore, given the uncertainty about the structural condition of the tree, what appropriate means of intervention might be used during its recovery period, including further specialist pruning and propping or other means of structural support.".

Public safety issues were identified and these were addressed during the initial phase of the project by excluding the public from the area within potential falling distance of the tree, whilst still providing reasonable visitor views. This was resolved by installing additional railings, with notices explaining the situation, not only safeguarding the public but conferring benefits for the tree by reducing compaction of the rooting environment from the public and from livestock.

Given the prestige and significance of the tree, the detailed condition assessment recommended that investment in its retention would be desirable, subject to evaluating appropriate measures to sustain and restore its condition in the longer term.

The feasibility of constructing a prop support arrangement was explored in detail together with consulting engineers to evaluate the tree's load analysis, wood condition and, using laser-plotting techniques, to map the trunk geometry. The unexpected conclusion was that installation of structural supports would not reduce (and might even increase) risk of further trunk fracture.

The conclusion determined that resources would best be directed towards Conservation Arboriculture measures to improve the health and vitality of the tree below and above ground.

Since 2012, a remedial programme has been underway involving a strategy to improve the ground surrounding the tree in order to optimise rooting conditions. This has entailed soil analysis, on which has been based treatment with woodchip mulch and compost tea.

The fencing has been upgraded to ensure the long-term permanent protection of the rooting environment by separating the public and livestock from the tree.

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A crown rejuvenation programme is also now in its third year involving specialist detailed pruning to reduce weight on specific branches whilst stimulating new growth in the lower canopy. This strategy is intended to create a future, more compact crown.

The history of the monumental Royal Oak will be secured for future generations by establishing and managing young oak regenerated from the aged parent.

"In simple terms," suggests Neville, "it is generally about putting together a robust arboriculture maintenance plan to safeguard the tree, in terms of its welfare and safety. This will be done by carrying out a number of operations that include seeing the tree, its roots and the soil as integral; in this case, through maintaining a healthy canopy and managing the ground conditions around the tree."