Symbolism, Imagery, Allegory
Valerian Street is a man who is used to controlling the world around him. As a rich candy maker, he has always controlled his employees, his servants, and his financial situation. The one thing he has never been able to control, though, is his son's heart. When Michael decides not to follow in his footsteps and run the candy factory, Valerian is disappointed. But that's nothing compared to Valerian's disappointment when he finds out that he'll never be close with his son emotionally or geographically.
As the book tells us, Valerian decides to build a greenhouse onto his vacation home at the same moment he realizes that he and Michael will never be close: "When he knew for certain that Michael would always be a stranger to him, he built the greenhouse as a place of controlled ever-flowering life to greet death in" (2.25). This line shows that there is a direct connection between Valerian's building of the greenhouse and his desire to control the world around him. Losing Michael has taken away his sense of control, but growing plants in exactly the way he wants to helps Valerian re-establish his sense of control over life around him.
As the novel unfolds, Valerian retreats into his greenhouse whenever he wants to be alone. On one occasion, Son comes into the greenhouse and speaks with Valerian. Son gives Valerian tips on how to make some of the flowers bloom. Valerian makes a bet with him: if the flowers die, Son gets booted out the door; if the flowers live, Son gets a brand new suit of clothes.
By the time we're halfway through the book, Valerian totally cares more about his plants than about his son not coming for Christmas. Although the household is getting pretty depressing when it becomes obvious that Michael isn't coming back for the holiday, Valerian is more concerned with the Yuletide behavior of his flowers, as evidenced by the fact that he says: "Christmas Eve's Eve and even the goddamn hydrangea had bloomed!" (6.1). You definitely know that the dude's priorities are always going to lie with the things he can control.
After he hears about Margaret's abuse of their son Michael when he was a baby, Valerian retreats to his greenhouse and barely ever leaves it, not even to bathe. He also lets the plants die and the whole house eventually becomes rundown.