What author's craft (like symbolism or perspective) does Harper Lee use to show moral courage in To Kill a Mockingbird?

One symbol of moral courage found in Harper Lee's To Kill a Mockingbird is the white camellia.

In Scout and Jem's neighborhood, Mrs. Dubose lives two doors to the north of the Finches and tends white camellia bushes in her garden. She is hated and feared by all the neighborhood children as the "meanest old woman who ever lived," and the children avoid going near her house like the plague (Ch 4). Yet, by Chapter 11, Scout and Jem grow old enough to decide it is time to walk into town by themselves, and they must bravely pass Mrs. Dubose's house in order to do so. Each time they pass, Mrs. Dubose hurls insults at the children. In Jem's mind, the worst insult she hurls is when she one day says, "Your father's no better than the niggers and trash he works for!" (Ch. 11). Jem grows so angry that he whacks all the white camellias off of Mrs. Dubose's bushes.

As recompense, Jem must go to Mrs. Dubose's house and read to her every afternoon. On his final day of reading to her, Mrs. Dubose says something very fascinating and unexpected to Jem:

Thought you could kill my Snow-on-the-Mountain, did you? Well, Jessie says the top's growing back out. Next time you'll know how to do it right, won't you? You'll pull it up by the roots, won't you? (Ch. 11)

One would not expect such a cantankerous old woman to give advice on how to kill her beloved flowers "next time," which leads the reader to wonder what her purpose was in saying the above.

Later, we find out exactly why Atticus wanted Jem to begin reading to Mrs. Dubose. Atticus explains that Mrs. Dubose had developed a morphine addiction due to the pain of her illness but felt determined to rid herself of her addiction before her death and wanted Jem to read to her as a distraction from her withdrawal symptoms. Due to her dedication to rid herself of her addiction, Atticus sees Mrs. Dubose as the "bravest person [he] ever knew" and wanted Jem to read to her so that he could "see what real courage is" (Ch. 11).

Interestingly, white camellias symbolize steadfastness and excellence, both qualities that are necessary in a brave person. In addition, camellias symbolize perfection and are given to someone you adore. Also, interestingly, Mrs. Dubose gives Jem a white camellia upon her deathbed. Hence, she is giving Jem a camellia to show that she appreciates his potential for steadfastness, excellence, and even bravery. Moreover, her gift to Jem of the camellia makes it evident that she advised Jem to pull the bushes up by the roots "next time" in order to encourage him to act upon his bravery to the fullest of his abilities, "next time."