Currently on iNaturalist the genus Salix has no subgeneric taxonomy despite having over 500 species. The big hindrance to adding subgenera and sections so far has been there there’s no source (as far as I know) that lays out the entire taxonomy for the whole world. There are only sources that cover North America, Russia and Europe, China, etc. separately.
We set up a Google Sheet that lists all the species, and started filling in subgeneric information for the first few. If you’re able to help, that would be awesome since there’s a ton of species: https://docs.google.com/spreadsheets/d/1ZyIyso9OonTZRhhne1cdZNWjUCRZP3IUX42J5EvuXAo/edit
Here are the main sources:
Russia, Europe, and nearby areas: http://www.herba.msu.ru/shipunov/school/books/skvortsov1999_willows_of_russia.pdf / http://126.96.36.199/announcements/Skvortsov1999.html
North America: https://www.researchgate.net/publication/250182087_Salix_Salicaceae_Distribution_Maps_and_a_Synopsis_of_Their_Classification_in_North_America_North_of_Mexico / https://cdnsciencepub.com/doi/pdf/10.1139/b76-297
Edit: Source that covers all of the above that I just found… http://www.fao.org/forestry/16387-064a6c432aa6ad67b71111974322d476f.pdf#page=81 / www.fao.org/3/a-i2670e.pdf#page=32
More discussion on the flag: https://www.inaturalist.org/flags/504010