What is the importance of Anya's winter garden in the novel, Winter Garden?

Anya has a rectangle of garden enclosed in an ornate iron fence that she refers to as her winter garden. Anya often spends time sitting and staring, or knitting in this garden despite the cold. Neither Meredith nor Nina understands Anya’s love for the garden because their mother cannot see color. Anya, Meredith, and Nina plan to scatter Evan’s ashes in the winter garden, but Nina trips and the urn shatters, flinging his ashes around the garden. Meredith and Nina are surprised when their typically cold mother leads them in laughing about what has happened.