September 1 is Wattle Day in Australia, the official start of the Australian spring. This is the time when many Acadia species (commonly called wattles in Australia) are in flower. So people wear a sprig of the flowers and leaves to celebrate the day.
Although the national flower is a particular species, named the golden wattle, (Acacia pycnantha), any acacia can be worn to celebrate the day.
The day was originally intended to promote patriotism for the new nation of Australia.
The push for the recognition of the nation-wide use of wattle was given momentum by the formation in 1899 of the “Wattle Club” in Victoria. It was initiated by Archibald James Campbell, a leading ornithologist and naturalist with a particular passion for Australian wattles, of which there are more than 1,000 species. For several years the club organised bush outings on the first day in September specifically for the appreciation of wattles in their natural setting.