In October 2016 I led a London Wildlife Trust walk supported by the Dulwich Society on the subject of Dulwich Park’s remnant boundary oak trees. 30 people attended a very lively and interesting event where we measured the girth of the English oaks (Quercus robur) and discussed their management and natural history. I’ve received a number of enthusiastic emails following on from the walk and firstly may I thank everyone who attended and contributed to it. The oaks of Dulwich Park are significant to London and could be afforded further protection and management consideration where possible.

Rural remnants

As former common and farmland, Dulwich Park is a remnant of the Great North Wood, a tract of woods, commons and farms that spread from Deptford to Selhurst, along what is known as the Great North Wood, a ridge of clay overlaying chalk and running between Honor Oak Park and South Norwood Hill. From Dulwich Park there are fine views of the Dulwich Woods straddling thie ridge, with the park residing low in the River Effra watershed. England’s parks, commons and wood pasture are home to many of our ancient and veteran oak trees today, with places like Epping Forest and the New Forest key reserves of ancient beech and oak trees at a national and European level. Oaks are significant trees not only in Dulwich but also in western Europe and the Americas. In Britain and Ireland, the timber from English and sessile oak (Quercus patraea) trees was used to build the ships which allowed the British Empire to ‘rule the waves’. Not even the entirety of Dulwich Wood and Sydenham Hill Wood (approximately 25 hectares combined) would have provided enough oak timber to build one of the great British ships as several thousand were needed. The reason why there are still oaks to be found in Dulwich is because these trees once had an economic and social purpose, perhaps even a spiritual one.

 English oaks were often planted as boundary trees between smallholdings or to demarcate the edges of ancient parishes. Indeed, a walk along Wood Vale in East Dulwich will reveal a line of old oaks which once set the border between the ancient parishes of Camberwell (now London Borough of Southwark) and Lewisham. There are individual oaks of past and present that are of local fame. The Oak of Honor gives the name to One Tree Hill and the now lost Vicar’s Oak, which once sat atop Anerley Hill before it was felled, just in time for the construction of the Crystal Palace in 1854, was a famous tree in Penge. These oaks were once part of ritual perambulations, whereby parishioners walked or ‘beat the bounds’ annually as local tradition. This is also where the name ‘gospel oak’ arises from, with prayers read out beneath the oaks during the traditional walk. London Wildlife Trust have tried to keep the tradition of beating the bounds alive with our Great North Wood walks over the past 35 years in Southwark.

What is a veteran tree?

The Ancient Tree Forum is the leading light in British ancient and veteran tree education and campaigning. It defines a veteran tree as one which is ‘big for the species’ and that is of high ecological and heritage value. In Sweden it is far simpler - ‘a tree that is very old, more than 1m in diameter at breast height or hollow.’ In Britain we consider a tree to be ancient if it is over 400 years old, which is also the same for our ancient woods. Veteran trees are interesting because they are often warped, battered and gnarled, not the lollipops that many of us were brought up expecting trees to look like. The ‘health’ of a tree can be highly subjective and the job of a local authority trees official can be very difficult. Making a sound decision about the management of a tree requires experience, understanding and a will to find the best solution for people and nature, not just Health & Safety box ticking or appeasing the whims of individuals.

The Dulwich Park oaks

The image below shows a line of three boundary oaks of great significance. There is the likelihood that a hedgerow once filled the space between these trees and was grubbed out to create sightlines, possibly as part of the formal park in 1890. The combined age of these trees is approximately 900 years.

The oak on the far left has suffered a hefty limb loss in recent years, opening up the core of the tree to decay, something that inevitably occurs in long-lived trees like English oak in one way or another. The tree has done something remarkable but not unusual for its type, putting out ‘aerial roots’ higher up the tree to feed on its own internal decay and thus reroute the nutrients available from the tissue. The reason the oak has become unbalanced is because it once was pollarded (cut at a height that grazing animals can’t reach with their teeth) but has not been pollarded probably since the early 1900s. This specimen has a girth of over 5.5m which means it is over 400 years old, using the measuring charts of the Ancient Tree Forum and VET project. Thoughtful management from Southwark Council has meant that the limb has been left and allowed to decay naturally, something seen across Dulwich and Belair Parks. The kind of internal decay found within veteran trees is crucial for a group of invertebrates that feed on this decay. Scientifically they are known as saproxylic invertebrates and they are the most threatened species community in the whole of Europe. Our native stag beetle is the only such beetle easily identifiable to most of us.

In Epping Forest experimental re-pollarding of similar oaks has drawn the conclusion that severe cutting leads to the death of the tree, due to a kind of shock. This is typical of old pollards across Britain, largely because of the end of the oak era in the 1860s when coal and gas became the most important sources of fuel and iron replaced timber in shipbuilding. Such factors led to the end of old fashioned woodland management.

The oak closest to the gate is a difficult one to age because it has a fair amount of extra wood that has been ‘put on’ by the tree over time, either from stress or internal fibre-buckling where the tree’s evident growth towards the light - phototropic growth - has meant it has become internally unstable and requires a process of realignment where the roots meet the soil. This oak is another lapsed pollard. This tree is likely to be between 250-350 years old. As I child I remember climbing this tree, inconveniently located next to the ladies’ toilets. Jokes aside, it is not an ideal place to loiter with a camera because the image that is really needed to show the scale of this tree would include the toilets as well. This image, however, still gives a sense of the tree’s size and shape. It is another lapsed pollard with large burring and bulgewood put on around the base of the trunk. The oak is an incredible 6.6m all the way around, putting the tree at an age of over 500 years. If that is correct, this tree has survived from the days of Dulwich Common being monastic land, through the dissolution of the monasteries, the English civil war, the Industrial Revolution, Napoleonic War and the World Wars. One note of caution is the amount of extra growth put on around the base of the tree, but even if this does superficially add on a century or two, the tree is still a magnificent specimen hailing from pre-industrial Dulwich.

One of the most famous oaks is the bulbous specimen located by the boating lake. This is also a tree that I remember hiding behind as a teenager on Friday evenings after school, usually having evaded a petty mugging or an attack from some rival school kids (we were from Forest Hill, so in enemy territory). It has a large girth of around 4m, meaning it is at least 300 years old. The tree is showing signs of stress and evident damage to the bark from dog urine where the tree is completely accessible. A simple knee-high fence as used for other oaks would suffice to start.

In this photo the exposure the tree is experiencing is evident, with signs of the damage being done to the bark at the base also clear. On closer inspection the bark looks to be breaking away in part. Oaks are hardy trees and can withstand damage. This leads on to considerations for the management of the trees.

This sizeable oak near the College Road entrance has a knee-high fence protecting it from vehicles creeping onto the grass. It’s a clever way to keep footfall back also, meaning that the tree can absorb oxygen through the roots via the soil because compaction is limited.

Saving our veteran trees

The next image is an example of sound management of our veteran trees. This oak lost a limb in a recent storm but the tree has not been felled on safety grounds. The tree is wounded, but the fallen limb has once again been left for those important decay-dependent insects and the tree is beginning a process of retrenchment, where the lateral buds latent in the bark (the tree’s leafy insurance policy) are coming into life and creating a new branch structure. This is thoughtful management from Southwark Council. Some of the most emotive responses to local authority plans relate to trees and green spaces, yet we continue to lose wildlife habitat which includes our veteran trees. The Forestry Commission estimate that London’s trees are worth £43billion in all they offer to our environmental, physical and mental health. This is an underestimate, as with the value of trees and nature it is largely a case of attempting to ‘quantify the unquantifiable’. We live in an age where money talks and even natural ecosystems, the most ancient ways of the world, are being earmarked for how much they are worth in economic terms. The value of the ancient and veteran oaks of Dulwich Park is great, relating to their ecology, amenity and heritage importance. But it’s not simply in Dulwich Park that these oaks are found, with future veterans in at least two other gardens subject to planning applications to have them felled. Veteran trees need management to keep them alive and organisations like the Dulwich Society, London Wildlife Trust and the Ancient Tree Forum campaign for their preservation. The efforts of Southwark Council to preserve these trees is crucial and should be recognised. They enrich our public and green spaces in ways we do not quite understand and harbour untold tales about the history of our landscape.

The biggest challenge facing our trees in 2017 is the lack of available funding for their care due to public sector funding cuts as part of central government austerity measures. There is less and less money to spend on trees, other than for the most basic safety measures, which sometimes are unnecessary. There is also less money to employ people to inspect and protect our trees, leaving them open to spurious safety claims from insurance companies and the like. This is where our veteran and ancient trees, unless they start causing trouble in their own way, could be forgotten. In this time of need it is up to local people to volunteer to find a way to celebrate and protect these irreplaceable symbols of our natural and cultural heritage. Every single tree mentioned in this article is unique and once gone, their stories are lost forever. Some of them could live to over 1000 years. We all need to work together to ensure future generations can experience these ancient trees.

Daniel Greenwood is the Manager of the Sydenham Hill and Cox’s Walk Nature Reserve administered by the London Wildlife Trust