Ash Trees in Jesmond Vale

Common Ash samaras or keys.

Ash trees lose their leave leaves early in the Autumn but their fruits or keys often persist through the winter. The leaflets of 3 – 6 opposite pairs have a terminal leaf. The leaves are phototropic turning to follow the sun. Gender is a complex issue in the Ash; a continuum between male and female varying with the age of the tree. Presumably the one in the photo is female.

Mature Ash bark

Ash can live for 400 years or longer if coppiced. The mature bark is attractively cross ridged.

Young trees have smooth pale grey bark which wrinkles as it ages.

Bark showing beginning of ridges.

Unfortunately Ash is susceptible to Ash Die-back Disease, also previously known as Chalara, caused by a fungal infection of Hymenoscyphus fraxineus, an ascomycete fungus. It is now present throughout the UK.

Infected sapling with characteristic lesion

It is most noticeable in young saplings, killing them quickly, although older trees take longer to succumb. The lesions form a diamond shape at first but spread around encircling the bark then killing the tree.

Extensive lesions on trunk

Fortunately, Ash has many genetic types, some producing Sercoridoid glycosides which may act as a defence. These glycosides may also be beneficial in combating the coming threat from the Emerald Ash Borer beetle.

Ash is the third most common tree in the UK providing a dappled canopy ideal for many woodland plants. Its loss would be devastating for the countryside and city green spaces.

White ash (Fraxinus americana)

There is an unusual large leaved ash growing in the Vale. It appears to be the White Ash (Fraxinus americana), a North American tree.

White Ash Leaflet

The leaflet turns a butter yellow in the Autumn and has 7-9 large leaves on leaflets. Some are in paired opposites others more alternate like the one above.

Top: Terminal and leaf scar of common ash. Below: terminal bud and leaf scar of White ash

Differences between common and White Ash are apparent from the buds and leaf scar. White ash has a browner, less smooth, terminal bud and the scar has a concave top edge.

White Ash bark is pale browny/grey with shallow parallel ridges

Reference:

http://www.mikepalmer.co.uk/woodyplantecology/docs/MNR-ashgender.pdf

https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/a-z-of-british-trees/ash/

https://phys.org/news/2020-11-chemical-clues-reveal-ash-tree.html

https://www.cabi.org/cabreviews/FullTextPDF/2019/20193167550.pdf

https://en.wikipedia.org/wiki/Hymenoscyphus_fraxineus

Collins Tree Guide 2004