During the Eocene, 50 million years ago, the wingnuts (Pterocarya) grew as forests throughout the whole of the northern hemisphere, but nowadays they are limited to Asia. However, they seem to be making something of a come-back in Finnish gardens.
The wingnuts are fast-growing, often with multiple trunks, and their dangling flower catkins can grow to half a metre. The common name derives from the seeds, which develop as small winged nutlets. The leaves are large, made up of opposite leaflets resembling those of the ash (Fraxinus), and turn a beautiful yellow in autumn.
The Chinese wingnut grows naturally throughout China except for the far north. The leaves are smaller than the other wingnut species; the central leaf rib is often grooved with two serrated flanges or wings, at least for part of its length. The species has thrived at Mustila since 1999, and may be slightly less susceptible to frost damage than other wingnut species.