In heraldry, in this case.
Searching for information about Lille and Flanders, I see that it has a
fleur de lys on its coat of arms. Wiki has a lot of info on this:
Fleur de lys - Wikipédia
I'm surprised that the seaside flower
Pancratium maritimum hasn't been incorporated into heraldry:
Especially in Brittany where it seems only to exist on one island:
Lys de Houat - Wildlife Photography
Of course, in Britain roses must be the most commonly used flower in heraldry?