I must begin this with wallflowers which was a flower my dad often grew in his garden. Perhaps it reminded him of home as I believe they are grown quite prolifically in England. They are certainly very beautiful.
Erysimum is a genus of flowering plants in the botanical family Brassicaceae (that must mean they are related to cabbages etc Now that is interesting). They are native to southwest Asia, the Mediterranean, Eutope. Africa, Micronesia and North America through Costa Rica. Many are endemic to small areas. Apparently wallflowers come in many colours but those that dad grew always seemed to be yellow or orange.
Wisteria also comes to mind although I've not grown it nor do I think I've ever seen it grown. Have seen lots of wisteria on film and have always though how beautiful it is. It is a genus of flowering plant in the pea family that includes ten species of woody climbing plants native to the Eastern United States and to China, Korea and Japan. Isn't this picture from Wikipedia beautiful.
I am sure there must be others but these are the only two I am aware of. If you know of other "W" flowers I would be interested to hear about them.
(thinking to self....I wonder if wisteria would grow in Perth?)