This quote references two of the narrator's character traits which would be paternal and protective, almost like he is alluding to a greater picture within the book.
This quote contributes to the overall theme of Puritanism and how the book is critical of the idea. The prison, a "black flower," is different with the bush as the prison penilizes, and the rose bush is kind.
Hester Prynne transforms shame into a symbol of individuality by wearing the letter “A”. The narrator connects the letter to nature with the word "fertile." Nature seems to be a big idea in this