Using similes, the story repeatedly compares Beatrice herself to the flowers of the garden. Watching Beatrice tend to the garden, Giovanni thinks she resembles them:
[...] for the impression which the fair sister made upon him was as if here were another flower, the human sister of those vegetable ones, as beautiful as they, more beautiful than the richest of them, but still to be touched only with a glove, nor to be approached without a mask.
The similes in the passage above not only compare Beatrice to the flowers in the garden in terms of her beauty, but also insinuate that she is just as toxic as they are. The simile comparing her to the "human sister" of the toxic flowers further highlights the notion that Beatrice resembles the flowers not just superficially, but at a fundamental level.
The story further accentuates this comparison through metaphors. In the same scene, Giovanni "almost doubted whether [Beatrice] were a girl tending her favorite flower, or one sister performing the duties of affection to another.” Again, this metaphor suggests that the toxic flowers are Beatrice's kin. These comparisons between Beatrice and the plants of the garden foreshadow the revelation that her body is poisonous.
