The greenhouse is a location in Mistilteinn.
The greenhouse is located in the proximity of the boarding house. It is implied it had never been used by previous squads from Mistilteinn, as Kokoro tells Mitsuru that she had to beg Nana to let her take care of the greenhouse. She also found some seedlings left behind and began planting them.
Kokoro tended to the flowers daily and Mitsuru soon began using it as a hiding spot to be left alone, and the two began spending time together in the greenhouse. Kokoro enjoys reciting the meaning of the flowers from her knowledge on the language flowers and she secretly plays with her baby doll in the greenhouse. Like the boarding house, the greenhouse is equipped with surveillance cameras.
It is in the greenhouse where Kokoro and Mitsuru’s relationship grows; they share their first kiss after Kokoro gives him a haircut, and she introduces him to forbidden concepts, such as intimacy. The flowers slowly start dying after Plantation 13, with the exception of Mistilteinn, is destroyed.
The greenhouse is a thin circular building with green and gray tainted windows. It is equipped with a water supply tank, which allows water to flow throughout the building.
There are several species of flowers in the greenhouse; from clockwise from the entrance/exit door, the flowers in order are: Marjoram, White Dendrobium Orchids, Cattleya, Cosmos, Evergreens, Blue-Purple Delphiniums, scarlet Argentea, Alocasia, Cosmos, Evergreens White Dendrobium Orchids, Bird of Paradise, and Marjoram. In the center is a small tree surrounded by red Hibiscus, Genista, Chlorophytum, and pink Begonias.
There are a few vases that contain cactuses, succulents, and lotus flowers. There are also lilacs in the greenhouse, which the squad places in one of the restricted rooms.
- The flower namesakes of Squad 13’s FRANXX are shown in the greenhouse: Strelizia Reginae, Delphinium x Cultorum, Celosia Argentea, Genista Cytisus, and Chlorophytum Comosum.
- Many of the flowers are foreshadows of Kokoro and Mitsuru’s relationship. See Trivia.