Explore the unparalleled floristic diversity of Arunachal Pradesh, a vital Indian biodiversity hotspot. This comprehensive botanical survey delves into the Upper Subansiri district, presenting a detailed taxonomic account of 1059 flowering plant species and 10 varieties. Essential for botanists, researchers, and students of Indian flora, this work meticulously covers topography, climate, vegetation, and economically important plants. It offers a crucial understanding of the unique phytogeography and botanical richness of Northeast India, making it a key reference for plant taxonomy enthusiasts nationwide.