Lilac
"No. Fire lilies are a symbol of the Fire Nation. If you won't have ice roses, then I will not have Fire lilies. This is a marriage between nations, Zuko."
"Well, if neither of us is going to have the traditional flowers, what are we going to do "You know what? Let's come back to the flower issue. All the other decorations are set. What should we do about the food?"
"Lots of chili flakes."
"Only if there are sea prunes."
"Sea prunes for an appetizer and your choice of meat with chili flakes?"
"Look! We can compromise."
"Your smile is beautiful."
Uncle Iroh walked into the room and casually interrupted. "You should have lilacs. It is the balance of yin and yang. Of your fire, Zuko, with your water, Katara."
The young couple smiled at each other. From then on, Zuko would bring Katara lilacs on their anniversary. At every event they held, there were lilacs. Even when they died of old age, buried side by side, their children would only ever bring lilacs to their graves. Their reign was written in history as the Age of the Lilac Monarchs. No Fire Lord and Lady before or after them was regarded with as much love as Zuko and Katara.