The Tea Girl of Hummingbird Lane by Lisa See. "Li-yan's family farms tea. Through a series of events, Li-yan separates herself from the rigid rules that have dictated life in their remote village. She has a baby out of wedlock and leaves it in a city. An American family adopts the baby and names her Haley. Haley is happy but wants to know more about her origins, and her mother aches to find her. They both go on a quest, and find the answers in tea."
