When Winnie lives with her aunts, she uses the greenhouse in the "western part" of the house as her hiding place. This greenhouse is symbolic for many reasons. First, it is symbolic of foreign influences on China in the twenties and thirties, because it was where Winnie's uncle had practiced one of his "English hobbies," which was gardening. Soon after the novelty of his new hobby has worn off however, the greenhouse is abandoned and used as a storage room for unwanted possessions. Winnie, while living in her Uncle and Aunts' house, feels unwanted and so she feels at ease among other "unwanted" things. She is also out of place much like "English hobbies" in China.
Furthermore, the greenhouse had once been a place for growth and, even if painful, Winnie does much "growing" of her own in that spot. Also symbolically it is where she can speak to her mother—it is where she finds a painting of her mother. One can even figuratively say that it is where her mother (this painting) "raised her." Thus, the greenhouse carries a great deal of weight and its symbolic power has many branches.
My Secret Treasures is the phrase that is written onto the box Winnie gives her daughter as a gift for her tenth birthday, which she finds full years later while cleaning her daughter's old room. Winnie had told her it was a place where she could keep her secrets and her "American" things. In a way, giving her daughter this box is like passing on the tendency to keep a secret life.
The statuette that Winnie creates at the end of the novel is symbolic of her own life and that of the Kitchen God's Wife. It is also representative of the power that Winnie has and that she has given to the character of the Kitchen God's Wife.