Places
The old oak that stands on the Green outside Oak Cottage is one of Leigh's most familiar landmarks, yet most of us pass it without giving much thought to its remarkable story. Robin Wood, who formerly worked for the National Trust and specialised in the care of pollarded trees, has taken a close interest in the tree, and his knowledge helps explain why it looks the way it does — and why it is likely to go on standing for generations to come.
Pollarding is an ancient practice. In mediaeval times, trees growing on common land were frequently cut back in this way, with the trunk severed at a height of eight or ten feet above the ground. The reason was practical. Grazing rights and the right to gather wood often belonged to different people, and new shoots springing up low on a trunk would soon have been nibbled away by livestock. By cutting above the reach of cattle and sheep, the regrowth was protected, and the fresh wood could be harvested by those commoners who held coppicing rights. The process would then be repeated every twenty years or so.
This treatment largely came to an end about two hundred years ago, when the Enclosure Acts abolished common land. Even so, many older trees continued to be cut back in the traditional way right up to the end of the Victorian era. The Leigh oak bears the marks of this long history of management.
Pollarding, far from harming a tree, can greatly extend its life. The explanation lies in how trees grow. The central heart-wood of any tree is dead; all new growth happens in the cambium, the living layer just beneath the bark. In an old pollard, the heart-wood gradually rots away, leaving a hollow cylinder of living wood. Far from being a weakness, this shape actually stands up to wind better than a solid trunk. That is why very few pollarded trees were destroyed in the 1987 hurricane, while so many mature trees elsewhere were uprooted. Our oak's hollow trunk, then, is not the result of a lightning strike, as some have assumed — it is the natural consequence of centuries of pollarding.
How old is the tree? Robin Wood estimates it at around 400 years. Judging the age of a pollard is not straightforward, because the central growth rings have long since rotted away, so a count of rings is impossible. Instead, an assessment has to take account of the soil type and the water supply. As a rough guide, the girth of a trunk at breast height equates to about one inch for each year, though this varies: trees grow more slowly on thin, dry soil, root competition and compacted ground both hold back growth, and pollarding itself slows a tree down because its crown is smaller.
A couple of years ago the Parish Council commissioned work on the oak. The heavy branches were cut back, and the ground beneath the tree was spiked and aerated. The road running beside the tree has harmed it over the years, because the weight of traffic compacts the soil in which its roots feed. The good news is that regrowth around the top of the trunk is already producing the branches that will one day replace those removed.
Such veteran trees matter for wildlife as well as history: pollarded trees are home to rare invertebrates, and it is recommended that large dead branches be kept near them. Robin Wood believes our oak could live for a further 200 years.