When Jim and Laura were in school together, Laura was weak and sickly. One day, Jim asked Laura what was wrong with her, and her reply, Pleurosis, was taken by Jim, who didn't know that word, to be 'Blue Roses', which he then called her as a nickname. Dramaturgically, this brief detail allows Williams to make some character points: Jim is popular but basically kind, Laura was shy, and the relationship between them was destined to be an unrealistic one, built on fantasy and misunderstanding. When they meet again in the Wingfield house, he bazrely remembers her, but she has added her memory of him to her "glass menagerie" collection of fragile fantasies.
Jim calls Laura "Blue Roses" because of an accident. Laura was out of school for a while, and when Jim asked why, she replied she had pleurosis. Although, he misheard her, and thought she said Blue Roses! The nickname stuck for the rest of high school. The nickname 'Blue Roses' is ironic because it is a perfect nickname for Laura. Most common roses, are red, just how most common girls act a certain way. Although, blue roses are unheard of and very unique, just like Laura who is not a common girl due to her differences.