For several decades, ecological studies have suggested that urbanized environments can be viewed asbiodiversity refuges, thus broadening conservation concerns from pristine to urban green areas. Despitethe increasing motivation to conserve areas where humans live and work, the conservation of urbanbiodiversity rarely takes citizens’ knowledge, perception, and needs into account. Interdisciplinary-basedconservation is thus urgently needed in order to bridge this gap. We therefore studied a park located inParis (France) where we combined ecological and human sciences to question a botanist and 100 parkusers about their knowledge and perceptions of plant richness. We then assessed the role of plant richnesson people’s perception of the services provided by the park. Our findings show that park users mainlyrecognized the cultivated plants promoted by gardeners, whereas the botanist more frequently observedspontaneous plants. Furthermore, the plant richness estimation by park users was much lower than thebotanist’s count. The users were attentive to the surrounding plant richness because of its beauty andits effect on their sense of well-being, whereas its role in biodiversity and ecological functions were lessrelevant. Finally, although the knowledge of plant richness among park users was poor and focused onornamental plants, they preferred to consider wild plant management in terms of cohabitation ratherthan removal, which may indicate a desire for more naturalistic landscapes. We discuss these resultsand propose several recommendations for improving biodiversity conservation in green parks withoutundermining the park users’ well-being.