In the final scene of the play, a seven-year-old Raynell runs out in her nightgown to see if her garden has grown. It hasn't. Of course, this isn't much of a surprise, since the girl just planted it the day before. Rose assures her, "You just have to give it a chance. It'll grow" (2.5.12). We're guessing this literal garden might just have some symbolic meaning.
For one thing, Raynell runs out to check her garden on the day of her father's funeral. Perhaps the garden represents the promise of new life in the face of death. Raynell herself is the flower that has sprung from Troy's seeds.
We can't help but notice that Raynell is looking at the garden just when another of Troy's offspring, Cory, enters. Cory is struggling desperately to escape the shadow of his father. Later in the scene, Cory's interaction with Raynell helps him come to terms with his father's memory. You could see Raynell's garden as representing the possibility that Cory will grow beyond the shadow of his father.