European ash (Fraxinus excelsior) is the third most common native tree in the UK, it is an important woodland and hedgerow species for both wildlife and timber production. Its leaf and canopy structure means that it naturally lets more light through to the woodland floor than other species such as beech, allowing other shrubs and ground flora to grow under its canopies, providing a more diverse woodland habitat.
In 1664, John Evelyn, a diarist and intellectual wrote Sylva, the first book published by the Royal Society. The book was a great success and encouraged landowners to plant woodlands and manage them for the production of timber, shaping many of the wooded landscapes we see today.
This is what Evelyn wrote about the ash: “In short, so useful and profitable is this tree, (next to the oak) that every prudent lord of a manor, should employ one acre of ground, with ash, to every 20 acres of other land; since in as many years, it would be more worth than the land itself.”
In the past, ash trees were thought to have medicinal and mystical powers, with the wood being burnt to receive prosperity as well as warding off evil spirits. In Norse mythology, ash was referred to as the ‘Tree of Life’. Even today it is sometimes known as the ‘Venus of the woods’.
The timber is very strong and good at absorbing shock, which is why it was so commonly used for tool handles and sports equipment (such as hurley sticks, used in hurling). Ash wood is also highly prized for use as firewood as it does not need to be seasoned and produces a good level of heat.
Unfortunately, there is a major threat to this fantastic tree species, which comes in the form of ’Chalara dieback of ash’; a disease caused by the fungus Hymenoscyphus fraxineus. The disease was first identified killing large numbers of trees in Poland in 1992, it then spread through much of Europe and was discovered in England in 2012 in Suffolk and Norfolk.
It is believed that the fungus’ native area is in Asia where the Asian species of ash are able to tolerate the disease through thousands of years of coexistence. Since the 2012 discovery, the disease has spread across the country and now is a common sight in most areas.
Chalara causes a loss of leaves, dieback in the crown and bark lesions in affected trees, this initial infection can make the tree more susceptible to other pests and pathogens such as honey fungus. The trees become very fragile as the structural integrity of the timber degrades and the risk of the tree snapping or losing branches increases.
Once a tree gets the disease there is no cure, however, some trees are showing a degree of natural resistance, which is the basis for a tree breeding programme with the aim of producing a population of ash trees that are tolerant to the disease.
At Englefield, ash makes up a substantial proportion of our broadleaved woodlands, not only in single-species plantations but more significantly as an integral part of mixed broadleaved woods, where they are growing with other species such as oak and sweet chestnut.
The challenge we face is a difficult one as there is a balance to be struck between retaining some ash trees to see if there is some genetic resistance to the disease and ensuring that the woodlands are safe places for people for recreation and work.
We are working closely with the Forestry Commission and Forest Research to look at the impact the disease has on the stability of the tree and the structural properties of the timber in a range of different aged trees growing in the open or in woodlands. This research will help to form advice to other landowners on how to manage ash trees and woodlands across the country.
To ensure that the woodlands are still safe places to work and for the public to enjoy, the Forestry Department will be assessing and managing ash trees in high-risk areas over the next year to reduce the risk to the public. This will involve the felling of trees in woodlands and along roadsides sooner than would normally be the case.
This will also provide the Estate with the opportunity to plant a wider variety of tree species to ensure that the woodlands are more resistant to future tree diseases. The trees for replanting will be chosen to suit the site conditions, but it is likely that they will include some species commonly found in the area such as oak, cherry, sycamore and lime as well as some more unusual species which are being looked at for future timber production such as walnut and hickory.
The loss of ash trees to Chalara is likely to have a larger impact than the loss of elm trees due to Dutch elm disease as ash is a more common species in the landscape.
Careful planning is needed to ensure that as many potentially disease resistant trees are kept as possible, whilst at the same time finding suitable species to replace the ash trees that do require felling.
Writer: Richard Edwards, Forestry Manager