The New Caledonian biodiversity hotspot is nowadays well renowned for its unique flora. In less than two decades numerous studies in various fields like geology, biogeography, systematics, phylogenetics, population genetics, centered onto New Caledonia have been published. From the identification of Amborella trichopoda as the sister species of all angiosperms to geological studies showing that New Caledonia was under water for millions of years, our knowledge and understanding of the highly endemic New Caledonian flora have considerably increased. Hypotheses explaining its origin and diversity have therefore dramatically changed. While new data and new studies are on the way to explain the dramatic in situ species radiations, and their adaptations to New Caledonian ecological specificities, the unique ecosystems encountered in the archipelago and their associated flora are facing major threats. Based on preliminary and partial IUCN evaluations from the local red list authority, about 40% of the 874 currently evaluated taxa are threatened. Invasive introduced deer and pigs, bush fires and nickel open mining activities are currently the main threats to species and plant communities. Ironically, while our plant diversity and diversification process knowledge get better and better, species extinction rate is rising.