Common or European ash (Fraxinus excelsior) Native to the British Isles and much of western Europe, except the far north.
Material from good quality British stands should be preferred, with provenances in northern France as an alternative in southern Britain.
Ash trees have intermediate shade tolerance when young, but they need early thinning for good growth. The species is cold hardy and moderately tolerant of exposure, but it is susceptible to late frost damage, which can cause forking.
This is a very site-demanding species. Grows best on moist, well-drained deep and rich soils with a high nitrogen content, and often overlying calcareous bedrock; requires pH values of 5 or greater. Nutrient-poor, dry and waterlogged soils should be avoided.
Pests and pathogens
In Britain, ash trees can suffer from a variety of root and butt rots that can cause late flushing, thinning foliage and decline leading to eventual death.
Ash can also suffer from a condition called ash dieback, involving the death of scattered twigs, branches or limbs, especially in the eastern drier parts of the country. It is commonly affected by ash bud moth (Prays fraxinella), which causes wilt and dieback of some small twigs.
The most serious form of ash dieback is caused by a fungus called Hymenoscyphus fraxineus (H. fraxineus), which used to be known as Chalara fraxinea (C. fraxinea). The dieback disease which this fungus causes is therefore sometimes called Chalara ash dieback to distinguish it from ash dieback caused by other agents. It has been causing serious damage to ash tree populations in Europe, including the United Kingdom, since the early 1990s.
Another threat comes from an exotic beetle pest, the emerald ash borer beetle (Agrilus planipennis) This pest is native to eastern Asia, but has been accidentally introduced to North America, where it is causing significant damage to North American ash trees. It is also expanding its range westwards across the Eurasian land mass, and has been recorded as far west as Moscow. There is therefore a constant risk that it will be accidentally introduced to the UK in wood imports.
A warming climate should increase the productivity of ash on suitable sites in northern Britain.
Ash is categorised as a Principal tree species. These are species which are currently widely used for forestry and will continue to be a dominant unless affected by a new pest or disease or adversely affected by climate change.