The seven evil spirits are not any kind of flowers among the four gentlemen. Four gentlemen refer to asparagus, green radish, cash cow and chlorophytum, which are common indoor foliage plants.
Seven evil spirits is a traditional geomantic term, which refers to the seven evil spirits in the yin house, including dark evil spirits, empty evil spirits, oblique evil spirits, trapped evil spirits, sharp evil spirits, narrow evil spirits and yin evil spirits.