Joe Starks symbolizes for Janie the horizon that Zora Neale Hurston references throughout the novel. The horizon, the farthest point one can see, is a place that holds Janie's hopes and dreams. 

In her first marriage to Logan Killicks, Janie is isolated on Logan's farm and is expected to labor in the fields with him all day. At night, when Janie looks at Logan in their bedroom, she is put off by his old age age and dirty feet. She does not find in Logan the "bee to her blossom" that she thought nature had promised her when she had her sexual awakening at the age of sixteen. 

Joe Starks meets Janie as she labors on Logan's farm and promises her that she'll never have to work like that again if she leaves with him. Joe is younger, "cityfied," well-mannered, and very ambitious. He tells of his plans to incorporate Eatonville as the first all-black town in America. Joe symbolizes to Janie a broader horizon and expanded dreams. She cannot wait to start a life with him and escape the confines of Logan's farm.

Once in Eatonville, however, Joe begins to control Janie and isolate her from her friends. And although Joe promised Janie an easier working life, she works tirelessly for the general store that Joe built in Eatonville. Their marriage wears away in misery for almost twenty years. The horizon that Joe represented was not as expansive and far-reaching as Janie originally thought.

The reasons for Janie’s separation from her first husband Logan and running with Joe Stark would help in the description of the symbolism portrayed by Joe.

Janie left Logan because of the passive lifestyle and although Logan was successful he was portrayed as a highly disciplined person whose life was a routine. Joe however was the opposite of Logan (at least when he is introduced to the reader) and he represented romance and thrill according to Janie. As the relationship between Janie and Joe progressed, Janie got to see the other side of Joe who was focused on living like the whites. His aspirations were predominantly superficial and materialistic, he was also selfish as portrayed through his relationship with Janie. He derived his happiness from showing off to the community and dominating his peers including his own wife.

Joe is the symbol of materialism and superficiality.

In Their Eyes Were Watching God, Jody (Joe) Starks is Janie's second husband.  When Janie meets Joe, she is still married to Logan Killicks, the man whom Janie's grandmother chose for her to marry.  Janie feels stifled in her marriage to Logan, so when Joe comes along, Janie sees him as a symbol for freedom and carefree living.  She runs off with Joe in hopes of finding a better life, one in which she would be able to explore her individuality.  However, once Janie and Joe set up their home and open the store, Joe becomes incredibly controlling and expects Janie to behave in particular ways.  He does not want her to be the object of desire for other men, so he has her hide her hair while in public.  Janie falls into depression under the rule of Joe, and her hopes and dreams of freedom are dashed away.  At this point in the story, Joe is no longer a symbol of freedom, but one of the dangerous pitfalls of hasty, impulsive action.  In the broader context of the novel, Joe may also be a symbol for male oppression of women.