An ash tree with the well-recognised winged fruit
When walking around Whiteknights campus you will see numerous Ash trees (Fraxinus excelsior), especially in the woodland of the Wilderness. These members of the Olive family (Oleaceae) are easily recognised by their toothed pinnate leaves and grey fissured bark. Many people will also recognise the species from the fruit; “helicopter seeds” or winged achenes known as “samara“.
Ash thrives in most landscapes and is the third most abundant species of broad-leaf tree in the UK. However the species could be in trouble with the recent discovery (February 2012) of the fungus Chalara fraxinea in East Anglia!
Ash Dieback is caused by C. fraxinea; a disease causing leaves to turn brown and the crown to die back. It has already wiped out 90% of all ash trees in Denmark and the discovery has raised fears of a repeat of the 1970s epidemic when Dutch Elm disease destroyed most of the UK Elm population.
A typical sign of infection is brown withered leaves.
In an attempt to stop the disease spreading, imports have been banned and the public are being encouraged to join in the battle against Ash Dieback with a smart phone app allowing users to submit photos and locations of sightings – http://ashtag.org/.
References:
Streeter, D., Hart-Davis, C., Hardcastle, A., Cole, F. & Harper, L., 2010. Collins Flower Guide. London: HarperCollins Publishers.
Rose, F. & O’Reilly, C. 2006. The Wild Flower Key (Revised Edition). Frederick Warne Publishers Ltd.