The Trees at Keele
Caucasian Wingnut Pterocarya fraxinifolia
Origin: the scientific name derives from the Ash-like leaves which are apparent in the photograph above. It is a relic of the Teriary flora on the southern flanks of the Caucasus Mountains and was introduced to France in 1784 but not until after 1800 in Britain.
Tree: it has an abounding vigour, stout shoots and large shiny green leaves and is usually planted near to water or in damp soils where it suckers easily; often forming a thicket.
It is unusual among hardwoods in that it doesn't have bud scales and is probably unique in that new buds arise from long stalks well above the leaf axil rather than in the axil itself.
The bark is a dull grey, with a network of broad vertical ridges. Like all members of the Walnut family, if you cut a small branch lengthways, you will find that the pith is divided into chambers - it is solid in all other families.
The leaves, which grow alternately on the stem, are compound in shape with and average of 20 leaflets arranged oppositely on the stalk. The leaflets themselves tend to be rather broad and floppy.
The female catkins are long and thread-like, between 25-50 cm, and strung with small seeds, each of which is surrounded by a whitish-green papery wing - hence the name.
Location : one below the dam between lakes 4 and 5; square R15.