Florence must leave home before she can leave her country to meet a man she's never seen before
Florence's life up until she decides to leave Lubbock for Egypt is an anti-pattern from that of her mother. Most importantly, the pattern begins when she talks her mother out of shooting herself after suffering a nervous breakdown due to a hormonal imbalance after her hysterectomy. This event is perhaps the most defining moment of her life so far. She is not athletic, but rather cerebral and bookish. She is unable to finish college and coincidentally find a secretary position in a cotton gin. Her attempts to meet and settle down with the right man fail, perhaps because she is looking for something (or someone that isn't there). She will grow to despise (but tolerate) the traditions of her roots, she will defy the expectations of her gender and race and she will seek the experience of the one constant and stable presence of love in her life, Shareef. She will discover that after she submits to intolerance, after she sheds her brown seed coat and harvests her true self.
It is important to demonstrate this anti-pattern as a foundational part of the plot leading to the climax, when Florence decides to finally write Shareef back and admit her failure. She will admit that it is time for her to leave her mother's fields and join the fibers of the global world (just as cotton is - or has been - a global commodity).
This leads to the over-arching connection between Florence's life, her mothers, the cotton plant and defoliation. Spiritually Florence is shedding the "daughter" coat and submitting her soul to the harvest, to leave home and travel across the globe to Egypt.
What needs to be worked out is the events around Florence's defoliation, her acceptance of her true fate: to travel to Egypt. She will grow tired of her mother constantly telling her that she's not doing things (like a lady). This is ironic because her mother was just as progressive when she was 18.