Tuesday, 18 December 2012

Week 2: Common Ash (Fraxinus Excelsior)

Common ash was @SpeciesofUK from 9th to 15th December 2012.

Common ash belongs to the genus 'Fraxinus,' a group of 50-odd species famous for their 'helicopter' seeds.1 It is one of the most (3rd or 4th) common trees in the UK, and one of the largest, growing up to 45m tall.

Common Ash
[Source: Jean-Pol GRANDMONT]

The UK has 80 million ash trees covering 5% of our woodland.2 Ash is such a good coloniser of open ground it has attracted the nickname 'the weed tree.'

Ash woodlands have light, open canopies, so are an important habitat for ground flora to flourish. Ash is one of the last UK trees to come into leaf, and one of the first to shed its leaves in the autumn.

Identifying an Ash

The bark is light-grey. It's smooth on young trees but rough and fissured on older trees

A distinctive feature of the ash is its 'pinnate' leaf made of 3-7 pairs of toothed oval leaflets, with a single leaf at the very end.

Ash Leaves
[Source: Jesmond Dene, Newcastle, Northumberland, UK; August 2005.]

Ash leaves can potentially be confused with elder and rowan. However, the rowan leaflets are narrower and more compactly arranged.3  One sure way to tell the difference is to check the branches. Ash branches are arranged opposite to each other, while rowan's are alternate.  The elder's leaves are again similar.  But elder has only 5-7 leaflets where ash has 7-15.4

Ash has black, sooty looking buds. They are visible from early winter and are very distinctive.

Ash WInter Bud
[Source: Botaurus stellaris]

Ash fruit are called 'keys' & are unmissable. The keys are the female flowers developed into fruits. They're called keys because they hang in bunches.

Ash Keys
[Source: Pleple2000]

Ash in Mythology

Pliny says snakes won't crawl over ash leaves & that a circle drawn using an ash rod will trap a snake.5

3 of the 5 sacred trees of Ireland were ash: The Ancient Tree of Dathi, The Branching Tree of Uisnech, and The Ancient Tree of Tortu.

In Norse mythology, Yggdrasil is the great ash tree that shelters & links all the worlds. Beneath Yggdrasil's three roots the realms of Asgard, Jotunheim, and Niflheim are located.6 The poem Völuspá tells us:

          An Ash I know there stands
          Yggdrasill is its name
          a tall tree, showered
          with shining loam."

[Source: Lorenz Frølich (1820–1908)]

Ash (or 'Ask') is also the name given to the first man in Norse mythology, who was formed from an ash tree.

Ash Dieback

Ash dieback is dominating the environmental news in the UK.  It is a fungal disease spread by spores. A tree must receive a lot of spores to get infected.7 The disease causes leaf loss and crown dieback in affected trees, and it can kill trees.

Ash Dieback
[Source: Courtesy The Food and Environment Research Agency (Fera), Crown Copyright]

Ash dieback was confirmed 20 years ago in E Europe. On 25 Oct 2012 it finally reached Britain.8 It has now been spotted at over 300 sites in the UK.

Ash in Use

Ash is ideal for staves and shafts - it is strong yet flexible, and when coppiced, produces long straight poles. Over time coppicing creates ancient ash 'stools,' or broad stumps of the original tree with many new shoots.

The wood of the ash was used by the Anglo-Saxons for spears and shield-handles. In Old English, a spear was called an ash or 'æsc.'9 Due to being tough and flexible ash has long found use in 'implements' eg oars, axe handles, hockey sticks, skis...10

Ash Oars
[Source: Motmit]

Strange but True …

As well as there being all male and all female trees, some ash trees produce both male and female flowers at the same time! In these instances, the male flowers only release their pollen once female flowers on same tree are no longer receptive, to avoid self-pollination.

Even more amazingly, ash trees can undergo gender reassignment. A single tree can produce all male flowers one year then all female flowers the next!

Ash Flowers
[Source: user:donarreiskoffer]


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