Why does the Little Prince cry when he sees the garden of roses? Does he have a reason to be unhappy?

The Little Prince cries when he sees the garden of roses because he thinks that his rose has lied to him. She had told him she was "the only one of her kind in the whole universe," but here was a whole garden filled with flowers that looked just like his rose! He also feels some pity for himself: "I thought I was rich because I had just one flower, but all I owned was an ordinary rose...That doesn't make me much of a prince." His tears are understandable, but misguided. He doesn't understand the nature of his love, or why she is unique. Of course, the prince will learn from the Fox that it doesn't matter whether there are other flowers that look like his rose -- what makes his rose unique are the shared experiences he has had with her. In fact, the prince can imagine exactly how his rose would react if she had seen the garden: he knows how she would cough and pretend to be ill to cover her embarrassment, and how he would work even harder to care for her. Far from being a reason for tears, the Prince will come to understand that such behavior is really a token of their love.