Alternatives to ash

Ash Dieback is now firmly entrenched in the UK and movement of ash planting stock is prohibited. This means that Chew Valley Trees cannot supply ash or ash cultivars, however there are a number of alternatives to consider if you were hoping to plant ash. Here's a brief overview of the problem and our suggestions for ash substitutes.

What is Ash Dieback?

Ash Dieback is a disease that can be fatal to ash trees (Fraxinus), caused by a fungus called Hymenoscyphus fraxineus*. Symptoms include dieback, brown/black blotched leaves and leaf loss, and diamond-shaped lesions where branches meet the trunk.

By blocking the tree's water transport system, the fungus can quickly kill young trees, or may take years to cause serious damage in older trees. Some trees may survive infection, or be resistant to it.

The disease was first found in the UK in 2012, having already infected swathes of trees across Europe. It spreads through wind-blown spores, which come from fruiting bodies on leaf stalks. These can travel both locally and over long distances - infection in the east of the UK may have been caused by spores carried on the wind from Europe.

Most parts of England, Wales and lowland Scotland have had confirmed cases and it is thought that 70-95% of our 90 million ash trees in the UK will be affected by the disease. This will affect our landscape, species that rely on ash, and cost society in terms of management of the disease, the expense of clearing up sick trees, and lost environmental benefits [1].

Note that it does not affect mountain ash, Sorbus aucuparia (also commonly known as rowan).

* The disease was formerly said to be caused by Chalara fraxinea, but this is the asexual form of the fungus, which doesn't seem to spread the problem.




Action against the disease

The key facts to remember are:

Legislation was passed in 2012 to prohibit imports of ash seeds, plants and trees, to limit the spread of the disease in the UK. A ban on internal movement was also put in place. So you can't purchase ash for planting in this country.
The spores come from fruiting bodies on ash leaves, so there is no restriction on movement of ash timber.
There is no immediate need to fell infected trees, unless they pose a danger.
Research has shown that some trees are resistant to the disease and may produce seedlings that are, too. In November 2019, a study was published showing which genes control resistance [2], so trees which could be used for selective breeding to help save the species can be identified.


Ash alternatives

Although there is thankfully hope on the horizon for ash trees, in the meantime, these are our suggestions for alternative native species to plant.

Birch

Both Betula pendula and Betula pubescens grow quickly, cast a light shade and produce a useable timber which can be used for firewood. It is possible to coppice them which means they could be put into a rotation otherwise they can be short lived.

Lime

Tilia cordata is currently an underused native species which grows quickly, at about the same rate as ash, but casts a denser shade. It can be coppiced and put into a rotation. If the requirement is for firewood is not as good as ash in this respect.

Hazel

Corylus avellana is a natural companion in this part of Somerset, good for all the same uses as ash, including being very good as firewood. It does not however make a large tree.

Alder

Alnus glutinosa is a dense, heavy wood which thrives on wet ground. It will grow in drier conditions, too. It is fast growing and will become a large tree, however it casts a denser shade than ash.

Wild cherry

Prunus avium is another native tree to consider, which is excellent for wildlife and produces a pretty blossom, though it can be susceptible to canker.

Further possibilities include oak, field maple, beech and hornbeam, though they can be damaged by grey squirrels, so if the aim is to produce timber this should be considered.



Refs:

[1] Hill, L. et al. 2019. The £15 billion cost of ash dieback in Britain. Current Biology, vol 29, 9: R315 - R316

[2] Stocks, J.J., Metheringham, C.L., Plumb, W.J. et al. 2019. Genomic basis of European ash tree resistance to ash dieback fungus. Nature Ecology Evolution (2019) doi:10.1038/s41559-019-1036-6