A veteran oak tree is usually somewhere between 200 and 400 years old. These are trees that have local historical significance or that play important roles in a particular biosphere or landscape. In the reserve we have many notable and veteran oak trees, numbered and mapped.
These are the survivors. Over the centuries, they have withstood changes to farming practices, forestry management and town planning. They have endured while the landscape has changed around them: streams have been diverted, old ponds filled in and new ones scooped out, hedges and water meadows grubbed up, neighbour elms and whole plantations of ash wiped out by disease.
These trees are the bones around which we are building the reserve’s biodiversity. As they age and decay they provide habitat for hundreds, maybe thousands of species. Looking after them and giving them the best chance to thrive occupies a lot of our time.
Haloing is an ongoing thing. It’s what we do when we have finished doing other stuff: we have drained the floodwater, picked up the litter, cleared the path; let’s go and halo an oak.
Haloing involves clearing the vegetation from around a tree to maximise the light its trunk and lower branches receive, and to reduce competition for space and nutrition from hedges, saplings and, here in the reserve, brambles.
We aim to clear beyond the tree’s drip line, the outer edge of its canopy where the water drips onto the ground. We use the trimmings to build a dead hedge, a barrier of branches and brambles around the tree, beyond the drip line, to protect its root zone. Root damage is a significant factor in an old tree’s survival. Almost 90% of a tree’s root system is less than 60cm below the soil’s surface, which means that footfall or a new path under an old tree can do a surprising degree of harm.
Oaks are slow movers, their life cycles spread out over centuries rather than decades. But after several years of diligent haloing, we can already see the effect: new growth on the lower branches of our trees. If we had let the lower branches die back, the trees eventually would have become top heavy and therefore vulnerable to high winds and storm damage.
Old oaks survive best if they die back from the top, with their centre of gravity dropping as they age. An ancient oak, one that has lived for more than 400 years, is squat and low to the ground, a monument to our landscape’s history.