The narrator's descriptions of Rappaccini's garden often portray the poisonous plants as if they are people. This use of personification sheds light on the idea that Rappaccini uses elements of the natural world in unnatural ways. When Giovanni sees the garden for the first time, the story includes the following observation:
The strange plants were basking in the sunshine, and now and then nodding gently to one another, as if in acknowledgement of sympathy and kindred.
In this description, the plants are presented as a sort of community, as if they enjoy each other's presence while also empathizing with each other. This, in turn, implies that there's something about their situation that is unfavorable or upsetting. They "bask in the sunshine," but they also feel a certain "sympathy" for one another, almost suggesting that they're somehow unhappy to be part of Rappaccini's garden. There's an implication, then, that nature itself has no interest in the malicious intentions of someone like Rappaccini, even if the plants are technically poisonous. After all, certain plants are poisonous for reasons of self-protection, which ultimately have nothing to do with the twisted experiments Rappaccini wants to the plants for. By personifying these plants, then, the story underscores the idea that what's truly unnatural about Rappaccini's garden isn't that it contains poisonous plants, but that he intends to use them to carry out twisted experiments on humans in the name of science.