In Saint-Exupery's The Little Prince, why does the prince think his flower is unique?

At first, the Little Prince believes his flower is unique. Then, the sight of the rose garden first leads the prince to believe that his flower is not, in fact, unique. However, with the fox's guidance, the prince realizes that even so many similar flowers cannot stop his own rose from being unique.

I believe this is an analogy for relationships everywhere between people. Think of it this way: a boy meets a girl and the girl becomes special to him. He may go to a party and see many other girls that are tempting to him who look equally attractive. However, after much thought, he realizes that HIS girl is special because she loves HIM.

I love this quote in the book,

"Men have forgotten this truth," said the fox.
"But you must not forget it.
You become responsible, forever,
for what you have tamed.
You are responsible for your rose. . ."

"I am responsible for my rose,"
the little prince repeated,
so that he would be sure to remember.

I believe that you become responsible for upholding the relationship with those that you love (or, as Antoine de Saint-Exupery says--those that you have "tamed").

 Thus, the Little Prince's rose IS unique because she loves him and he loves her. This makes her different from any other rose in the garden.