Losing the canopy

ash canopyNext time you walk down the Wild Garden Avenue towards the Round Pond, pause at the junction of the path that goes off to the left. Take a look at the trees in the fork of the junction, a stately cypress standing as a sentinel. Just in front of this is a straight and rather boring looking tree trunk.

But look up and you will see the magnificent crown of the ash, rising some three metres above the other trees and casting a dappled shade below it. The leaflets move in the direction of sunlight, varying the amount of light that reaches the next layer down. This is the ash canopy, common throughout the UK and steeped in history and mythology. The ash is the most numerous of the trees in the Garden, making up around 30 percent of the mature trees, some 325 trees.

And we are about to lose it! Like so many woodlands in the UK we are now suffering from Ash Dieback, also known as Chalara dieback. Ash dieback causes trees to lose their leaves and the crown to die back, and usually results in their eventual death. First identified in Poland in 1992, the disease spread to the UK in 2012 and spread rapidly. There is now nothing we can do to slow down or stop the destruction. At present many of the ash trees in the Wild Garden are showing some signs of the disease, mainly in their branches but in time the main canopies will also die.

So what to do? At present our management approach is to monitor the trees that may present a risk to the footpaths and cut back dead branches. But this will only work for a couple of years. We will then have to start felling the affected trees, changing the shape and views of the Garden for ever. Overall, we can expect to lose some 70% of the ash in the Wild Garden, over 200 trees. Ironically, in some cases it will bring the tree-scape back to the Victorian planting since many of the ash are self-seeded.

Losing the canopy will affect the woodlands in a number of ways. There may be more sun light at ground level but this will not necessarily help some of the plants or insects that thrive in the shade under the ash. Some of the evergreens will come to the fore, given more space to expand and some of the second-tier trees will be able to grow, but only time will tell.

So let’s enjoy the canopy while we can, look up and admire the ash – for so long a part of our heritage, mythology and industrial use. And let’s hope that some are resistant enough to survive.

Mike Watson

February – March 2020