Tree a Week: Ash

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Ash Tree {Fraxinus excelsior}, Peak District National Park, UK, Derbyshire

Characteristics and Interesting facts

  • The Common Ash of the Fraxinus excelsior genus is in the olive and lilac family, Oleaceae. There are around 65 species of medium to large trees, the majority are deciduous however there are a few evergreens and subtropical species.
  • Ash dominates most of the British woodland, it’s the third most common tree in Britain and is widespread across much of Europe, Asia, and North America.
  • Ash is the UK’s tallest native deciduous tree when fully mature, it can grow to be as tall as 35m and can live up to 400 years, and longer if coppiced. It is also one of the toughest hardwoods and absorbs shocks without splintering.
  • Ash is invaluable to a lot of wildlife providing ideal habitats for numerous species, the leaves offer excellent food source for many varieties of moth and caterpillars. It’s also a very important tree for lichens, in the UK 536 different lichens (27.5% of the British lichen flora) have been recorded growing on it, including a number of rare and endangered species.

Threats

Across Europe and the UK the future of the ash has been under threat due to a fungal disease, Chalara fraxinea commonly known as Chalara ash dieback. Symptoms of the disease include cankers, wilting, loss of the leaves and the die back of the crown usually resulting in their death. There is no known treatment or cure at present, although some trees appear to have resistance to the disease.

Fungal relationships: In contrast to many tree species, ash does not form ectomycorrhizal associations with fungi, where the fungal hyphae surround the roots of a tree without penetrating them, exchanging nutrients, and producing the familiar mushrooms that fruit near the tree. However, ash does form arbuscular mycorrhizal symbiotic relationships with fungi, in which the fungal hyphae penetrate the tree roots, enabling a mutually-beneficial exchange of nutrients to take place, but these fungi do not produce visible above-ground fruiting bodies.

The shaggy bracket fungus (Inonotus hispidus) is parasitic on ash trees, causing white rot in the heartwood, and leading to the loss of branches and major limbs. Dead ash wood is the habitat for a distinctive saprotrophic fungus called King Alfred’s cakes (Daldinia concentrica), which has black, ball-shaped fruiting bodies.

Uses

  • Common ash wood is commercially highly valuable due to its pressure, shock and splintering resistance and elasticity and hardness. It is used for making tool handles of all kinds; sport handles such as snooker cues, and baseball bats.
  • Additionally, before the use of steel ash was widely used for weapon handles, agricultural implements, carriages, cars and boat frames. A desirable wood used for veneers furniture and flooring because of its straight grain and consistency with sapwood and hardwood differing little.
  • Various parts of the ash are used for food: seeds, shoots, leaves and sap. Ash keys (the winged seeds) have been eaten as a pickle in Europe and Asia. The young shoots are edible and can be added raw to salads, the leaves have been used for tea and the tree sap can be tapped to make ash wine.  Check out this site for pickled ash key recipe.

Identification:

Leaves: Fraxinus excelsior consist of 3-6 pairs of light green, serrated and stalkless oval leaflets which can grow as long as 40cm, with an additional singular leaflet at the end. Sometimes the whole crown of the tree will lean in the direction of the sun, this is due to the leaves moving in the direction of sunlight. Another characteristic of ash leaves is that they fall when they are still green.
The leaflets are slightly toothed on their margins and are dark green on their upper surface; the undersides are a paler yellow-green. The leaves are amongst the first to fall in autumn, and turn a relatively inconspicuous yellowish green before doing so.

Bark: The bark is pale brown to light grey when young with a smooth surface that is often covered with lichen. As a tree ages, the bark will become thicker and vertical fissures will form. Easily identified in winter by smooth twigs that have distinctively black, velvety leaf buds arranged opposite each other.

Flowers: Ash is easily identifiable in the winter due to its distinctive black flower buds which stand out in contrast to the paler twigs. The flowers open before the leaves unfold. Ash is dioecious, meaning that male and female flowers typically grow on different trees, although a single tree can also have male and female flowers on different branches.

Fruits: Once the female flowers have been pollinated by wind, they develop into winged fruits, or ‘keys’, in late summer and autumn. The fruit, or seed, each has a single long wing that drops in autumn called an ash key, which hang in great bunches and aids wind pollination.

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