In Oscar Wilde's story, the Student laments that there are no red roses in his garden. He insists that he cannot court a woman successfully without one. The Student desperately wants a beautiful lady to dance with him until dawn at the Prince's ball.
In the story, we learn that the Nightingale sacrifices her own life in order to grow a beautiful red rose for the love-sick Student. Her lifeblood ebbs away as the thorn pierces her heart. However, when the Student presents the rose to his favored lady, she scorns his gift. She rudely tells him that the rose will not match the color of her dress. Furthermore, she relates that the Chamberlain's nephew has already sent her "real jewels." She has no real use for a flower. To the beautiful girl, the rose (although obtained at great cost) pales in comparison to sparkling gems.
As for the Student, he becomes angry after hearing the girl's words. He immediately throws the rose away, and it falls into the gutter. His reaction demonstrates his shallow view of love. He has mistaken infatuation for true love. The beautiful girl makes the same mistake. She thinks that the Chamberlain's nephew will be a better catch for her, so she rejects the Student.
Her behavior leads the Student to conclude that love is "silly," "quite unpractical," and "not half as useful as Logic." However, the truth is that the Student does not really comprehend the meaning of true love. This is why there are no red roses in his garden. The red rose is a symbol of sacrificial love, of which the Student has neither the comprehension nor the character to grasp.