Koelreuteria paniculata (Goldenrain tree). Also called the India Tree, the Varnish Tree, the China Tree, or the Chinese Scholar Tee.
The Goldenrain tree is native to Eastern Asia and appears to be distributed mostly in the eastern temperate half of China, and especially in Central China, found in smaller populations in the Korean peninsula, along the coasts bordering the Yellow Sea and in a smattering of places on Honshu island. They are usually found around tomb areas, shrines and temples, giving the suggestion that the seeds or seedlings must have been dispersed by people or animals from elsewhere. In Japan, tradition has it that the tree is often planted over the graves of scholars. The tree has traditional medicinal uses for treatment of eye problems (ephiphora and conjunctivitis) which may be why it was traditionally grown around scholars (many whose eyes must have been saved by the tree in ancient times).
In China, the trees are known as ‘Luan’ or ‘Luan-hua’. The flowers are used by the Chinese to make a yellow dye and traditional medicines. The leaves are for dyeing black and the seeds are made into beads.
More recently, Chinese researchers have found that Goldenrain trees planted in abandoned mining areas actually remove heavy metals from contaminated soils while beautifying the landscape.
It is today commonly grown as an ornamental garden tree.
Sources and readings:
Chinese Medicinal Herbs: A Modern Edition of a Classic Sixteenth-century Manual by Shizhen Li, Porter Smith, George Arthur Stuart, pp 227-228.