Willows are very cross-fertile and numerous hybrids occur, both naturally occurring and in cultivation. A well known example is the Weeping Willow (Salix × sepulcralis), very widely planted as an ornamental tree, which is derived from hybridisation between the Chinese Peking Willow and the European White Willow.
Described as “weeping”, it is so true to nature, just like what we said: 江边一树垂垂发。