Came across this impressive Caucasian Wingnut (pterocarya fraxinifolia) in the garden of the Rijksmuseum in Amsterdam.
I really don’t know much about the specie, but I loved the ruggedness of its trunk contrasting against its soft foliage. Plus it was one of only a handful of large trees around the central Amsterdam. For such a green city, there were many old trees, at least not where I wandered.
Further reading revealed this particular tree is related to the walnut family. Indeed, the specie bears many similarities to the Black Walnut (juglans nigra), which also sports a rough, ridged bark. The name caucasian is indicative of its origins in Eastern Europe and Turkey.
I have yet to spot one in Hong Kong, at least not one I recognised.