What Tree? Ash

Ash (Fraxinus excelsior)

One of the most widely spread trees in Europe, the ash tree can be found across a vast area ranging from the UK in the north, to the coast of North Africa and east as far as West Asia. It is native to the UK, having established itself after the last ice age, approximately 7000 years ago. It is commonly found across much of the UK, and where it grows in woodlands, it is often associated with oak trees.

As a species, ash can grow up to 30m in height, with a crown spread of 20m. One of the most prominent features of the tree is the grey colour of the bark (some say the origin of its name comes from the comparison between the bark colour and that of ash found in fires). The growth habit tends to be wide and open, but with long, sweeping, ascending branches.

It has a compound leaf (the leaf itself consists of several leaflets), with up to 13 pairs of leaflets coming from a central stem (rachis). This stem always ends with a terminal bud. The leaves are among the last to emerge in spring due to a requirement of high levels of light (longer days) to initiate bud burst. They are among the first to fall in autumn. Unlike many deciduous trees, the leaves of an ash tree do not change colour in autumn.

In winter months, the ash is one of the most easily identifiable trees, with the buds being a distinct black colour, and often referred to as being shaped like a bishops mitre.

Pests and Diseases

Ash is susceptible to several diseases and has a reputation for brittle wood that fails easily. This perceived failure of the wood strength means it tends not to be a popular garden tree, but is a woodland favourite for the quality of timber it produces. The more common diseases to be found on ash include King Alfred Cakes (Daldinia con-centrica – small, black, cake-like fungal bodies that live on dead wood) and the shaggy bracket (Inonotus hispidus – an orange brown bracket (black in maturity) commonly found on large branches/stems, which can cause structural instability). Honey fungus (Armillaria species) is also known to infect ash trees, but healthy trees are also known to show tolerable resistance to infection.

Ash Dieback

Ash dieback, commonly referred to as Chalara Ash Dieback is a fungal disease that affects the ability of the tree to transport water, nutrients and sugars, all ingredients vital to its survival. Ash as a tree species is a vital part of the UK landscape and biosphere, home to over 1000 organisms, and a vital timber crop in the forestry sector. Ash dieback weakens the ability of the infected tree to fight off secondary pathogens that can then go on to kill it.