From its first episode, Darling in the Franxx uses flower language and plant genetics to frame the entire series. It’s not subtle about any of these trappings, which continue to appear in each passing episode week after week not only in commonly-used titles (like pistil, stamen, etc.) but also in flowers found in the on-site greenhouses, in various rooms, and the series’ most recent ending sequence.
The chrysanthemum and cherry blossom are both national flowers of Japan. They’re also the names of the two plantations that “kiss” in Episode 5 of Darling in the Franxx, bringing two teams of parasites together.