Based off Cassandra Jean's flower cards for the Shadowhunter series (you can view them here: http://shadowhunters.wikia.com/wiki/Cassandra_Jean )
Floriography, however, is much older than that. It is approximately a thousand years old, but it recieved the most interest in Victorian England. Basically, it is giving flowers meanings, and that can then be given to various characters, like Cassandra Jean did there. I thought most of the Balto characters have traits that could be connected with various flowers, and I thought why not. The first one was chosen to be Aleu.
So why yellow carnation? Well, its meaning is Rejection or Dissapointment, and I think it fits Aleu quite well (and Balto, too, but he will get a different flower). She was cast out by the humans and not adopted because she looked like a wolf, and when she found out she indeed was a part wolf, what else did she feel than rejection and dissapointment.
Original idea (c) Cassandra Jean
Aleu (c) Universal
Drawing (c) me