I want to give a brief resumé of the reasons why the taxonomic study of Salix is so notoriously difficult. As long ago as 1737, Linné in Flora Lapponica wrote: “Hunclocum sibi postulat Salicum familia, qui si ulla in Botanicis obscura, haec sane maxima”. The phrase “crux et scandalum botanicorum” has been quoted time and again.
(1) All willows are dioecious, developing male and female flowers in different individuals.
(2) Flowers in many species are precocious, the flowers appearing before the leaves.
(3) There is a tendency for the current year's terminal and past year's lateral branches to differ in indumentum, leaf shape and leaf sequence.