What do apples represent?

Generally, apples symbolize love. They commonly appear when speaking of Sanji and her companion. Sanji offers her companion an apple which she has sliced and prepared, thus showing her love. Later, the Strange Bird is taken to an apple tree after each modification to show her that Sanji cares for her. At the end of the novel, the Strange Bird comes upon a copse of apple trees which foreshadow the appearance of the other Strange Bird.