As Nanny speaks to Janie, after the young woman kisses Johnny Taylor over the fence, she uses a complex metaphor:
You know, honey, us colored folks is branches without roots and that makes things come round in queer ways. You in particular. Ah was born back due in slavery so it wasn’t for me to fulfill my dreams of whut a woman oughta be and do.
Nanny then goes on to discuss how she wants Janie to try to make something of herself, rather than kissing men she doesn't approve of over the fence. Metaphorically, Nanny says that "colored folks is branches without roots," describing that the history of slavery has made it difficult for Black families to develop respect, dignity, and social position over the generations. Nanny lived through slavery—the only character in the book who did—and therefore has special knowledge of this condition. This is one of the rather few descriptions of racism in the book. In general, Their Eyes Were Watching God is not a story about race or racism and is instead merely a coming-of-age story framed around three romances, that happens to include almost exclusively Black characters. This metaphor from Nanny, though, is one of the few specific descriptions of racism in the book.
This metaphor extends, or perhaps contradicts, another one from a few pages before: "Janie saw her life like a great tree in leaf with the things suffered, things enjoyed, things done and undone. Dawn and doom was in the branches." Janie sees her life in all of its branches, spreading out in possibility. But Nanny reminds her that because of her race and gender, that tree is without roots, able to be blown and changed by circumstance. (Nanny, of course, turns out to be right, as Janie is tried unfairly, though eventually acquitted, for Tea Cake's killing at the end of the book.)
The extension of this metaphor also draws attention to the structure of the book and its frame story. In the order of the book as it is read, it appears as if Nanny's metaphor is an extension of Janie's, since Nanny's metaphor comes after Janie's in the novel. But in the actual chronology of the story, Janie's calls her life a "great tree in leaf" while speaking to Pheoby, some 20 years after Nanny tells Janie that "colored folks is branches without roots." So Janie, really, is extending Nanny's metaphor. Janie likely is remembering Nanny's old statement some 20 years later and incorporating it into her understanding of her own life.
As an older Janie works in Jody's store in Eatonville, she starts to find the work not grueling, but certainly tedious. That feeling is described in a long and descriptive metaphor:
The store itself kept her with a sick headache. The labor of getting things down off of a shelf or out of a barrel was nothing. And so long as people wanted only a can of tomatoes or a pound of rice it was all right. But supposing they went on and said a pound and a half of bacon and a half pound of lard? The whole thing changed from a little walking and stretching to a mathematical dilemma. Or maybe cheese was thirty-seven cents a pound and somebody came and asked for a dime's worth. [...] That was the rock she was battered against.
The final sentence of this paragraph is the metaphor: "That was the rock she was battered against." The rock, then, is the combined effort, annoyance, and pain of all these menial tasks in the shop: math problems, heavy lifting, awkward action. It is a rather unusual structure, on the sentence level, for a metaphor: there is a long description of the experience of running the shop after 20 years, its inane and frustrating tasks, and only at the end is that whole description swiftly collected in the image of a body battered against a rock by the sea.
This construction gives Hurston the opportunity to provide elaborate background of the general store and Janie's work there. But the metaphor of the rock, so short after such a long paragraph, shows how even such a complicated job becomes so mundane over time. Janie feels as if she is battered into a rock by the sea over and over again, much like how her job feels the same every day—despite the complexity and intricacy of the description of the job in this paragraph. This makes an interesting contrast and shows just how bored Janie is with her job. On a subtler level, as well, the image of the sea beating against the rocks gives quiet foreshadowing for the encroaching Lake Okeechobee later in the novel.