This is a very rare purple form of the common walnut (Juglans regia). It is not even mentioned in many tree books and the Belfast Botanic Gardens specimen is one of the few illustrations of this plant in Google Images. It is slow growing but should eventually make a handsome small tree of about 10m (some nurseries give a figure of 4m for height while other sources suggest they can reach 20m). The leaves are blotched with red and the husks of the nuts are a deep red. The large buds, in common with the species, are a buff colour making them easy to distinguish from ash (Fraxinus sp) which has black buds. The aromatic leaves secrete a toxin which can kill herbaceous plants planted under walnut trees.

Photos taken in Belfast Botanic Gardens in 2009. Copyright: Friends of Belfast Botanic Gardens.