Friends of Allestree Park

Allestree Park in Derby, England

Ash Die-back by Bill Grange

The Ash Tree - Description

ash composite reducedThere are many species of ash, but the only British wild ash - and the one overwhelmingly encountered here - is the European Ash, Fraxinus excelsior. Please don't confuse true ashes from the Rowan, also called 'Mountain Ash'. This small tree with smaller leaves and red berries is botanically not an ash and is in a completely different family.

European Ash is a deciduous tree, growing to 20–35 metres (exceptionally to 46 m) tall with a trunk up to 2 metres (exceptionally to 3.5 metres) diameter, with a domed crown. The bark is smooth and pale grey on young trees, becoming thick with deep vertical fissures on old trees. The shoots are stout, greenish-grey, with jet black stout buds – a very characteristic feature in winter.

The leaves are 20–35 cm long, consisting of 7-13 leaflets coming off a main stalk (a situation called 'pinnate'). The leaves are often among the last to open in spring and the first to fall in autumn if an early frost strikes. The Ash is not noted for its autumn colour, the leaves turning a paler yellowish green before falling. The flowers open before the leaves, the female flowers being somewhat longer than the male flowers; they are dark purple, and without petals, being wind-pollinated. Both male and female flowers can occur on the same tree, but it is more common to find all male and all female trees. The dry fruit, the ‘ash key’, has a single wing, often hanging in bunches through the winter.

European Ash rarely exceeds 250 years of age. However, in Britain, there are many estimated to be between 200 and 250 years old and there are a couple over 250 years.

What is Ash die-back?

Die-back of ash is a serious disease of ash trees caused by a fungus called Chalara fraxinea. The disease causes leaf loss and crown dieback in affected trees, and it can lead to tree death.

Outbreak

Ash trees suffering with C. fraxinea infection have  been found widely across Europe since ash trees were reported dying in large numbers in Poland in 1992. These have included forest trees, trees in urban areas such as parks and gardens and also young trees in nurseries.

In February 2012 the infection was found in a consignment of trees sent from a nursery in the Netherlands to a nursery in Buckinghamshire. Since then it has been found in a number of locations in England and Scotland, including a car park in Leicester; a Forestry Commission woodland in Scotland near Glasgow, west of Glasgow; a college campus in South Yorkshire; and a property in County Durham. All these sites had received stocks of young ash plants from nurseries within the past five years.

In October 2012, a small number of cases were confirmed in East Anglia in ash trees which did not appear to have any association with recently supplied nursery stock.

 

What are the symptoms of Chalara fraxinea?

The leaves develop dark patches, which then spread to twigs and branches. Cankers then emerge on branches. However, all of these symptoms could be caused by other problems, so final diagnosis should be made by an expert.

 

What National Impact will the disease have?

Ash is a very important tree, both for it’s landscape value and wildlife. It is particulary common along roadsides and as a field tree. It is a major constituent of many woodlands and in some area, including the limestone area of the Peak District, such as Dovedale, Miller’s Dale. etc., the woodlands are mostly composed of ash.

Ash is an important tree for wildlife. It is very long lived, enabling it to support many species of wood-eating insects such as the lesser stag beetle and hole nesting birds such as owls and woodpeckers.

Ash woodland has a light open canopy which encourages a rich ground flora of dog’s mercury, bluebells and ramsons. It is usually accompanied by a hazel understorey.

The alkaline bark of ash supports numerous lichens and mosses. The leaves provide food for the caterpillars of many moth species including the barred-toothed striped, the coronet, the brick, the centre-barred sallow and the spectacular privet hawk moth. Birds, such as the bullfinch, eat ash seeds.

Upland mixed ash woodlands, such as those of the Peak District form one of the richest habitats for wildlife, sheltering many rare woodland flowers such as dark red helleborine, Jacob’s ladder, autumn crocus, lady’s slipper orchid and threatened butterflies such a the high brown fritillary, the dingy skipper and the grayling.

What impact will the disease have on Allestree Park?

At the time of writing, no cases had been found in Allestree Park but, many people fear that it won’t be too long before it is.

Ash isn’t very common in the largest woodland in the Park, Big Wood, because the soil there is rather too acidic for it. However, the Ash is very common in the central and eastern parts of the Park, where it occurs in the woodlands there. There are also a number of  fine specimen ashes in more open situations. If the ashes in the park were all to disappear the impact on the Park’s  landscapes and wildlife will be great.

Please keep a close eye on ash trees when out in the Park and report any ashes you think may be infected. 

Who should be notified?

If any diseased ashes found in Allestree Park (there were no cases up to December 2016) and other of the City’s Parks, Derby City Council Tree Officers 01332 641574 and the City Council’s Parks Dept. 01332 293111.

ash stem showing infection

 

 

 

 

 

 

 

Stem of infected ash, showing lesion

 

 

 

 

ash die-back distribution 2012

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Distribution of known outbreaks of Ash Die-back, late 2012

 

 

 

  

 

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A Tribue to the Ash Tree

Click on the button for a sideshow - 'A Tribute to the Ash Tree' - showing how the Ash is so important to the British landscape, mainly Derbyshire. When you reach the site, click on 'slideshow at the top left.

 

December 2016: Some cause for optimism? Click on the link below for an article from The Guardian:

 Ash Die Back - latest news

 

 

Thursday, November 23, 2017