I am a bit late with this post as ANZAC day in Australia is on April 25th, however I am going to continue as I think this is something that a gentleman (or lady) can adopt that has all the savoir faire in the world.
For those of you outside of Australia ANZAC stands for the Australian New Zealand Army Corp and ANZAC day is a national day of remembrance in Australia and New Zealand that commemorates those that fought in Gallipoli Turkey during World War I. It now more broadly commemorates all those who died and served in military operations for their countries.
A wonderful tradition is the wearing of small sprigs of rosemary in the coat lapel as a sign of remembrance and commemoration. My mother still has growing in her garden a rosemary bush that is over 50 years old taken from a sprig of rosemary that was worn by my grandfather in an ANZAC parade many years ago.
Now that the weather is getting cooler and men will be donning jackets once more I think nothing cuts more of a dash than wearing a boutonnière. However, nowadays flowers generally seem to be regulated to weddings and can be a little too formal. Instead grab a single herb and pin it to your label as below. Mint or lavender as does any herb looks fantastic. I always try and pin a little something on a lapel if I am wearing a jacket.