The present investigation is an attempt to study the uses of ethnomedicinal plants in traditional knowledge system among the Assamese community of Dibrugarh District in Assam.  All the relevant data were collected during 2017–2019 by following standard ethnobotanical methods through personal interviews as well as through focus group discussions with a total of 193 informants including 62 men and 131 women.  The use value (UV) of the medicinal plants and informant consensus factors (FIC) values were determined.  In the study 174 ethnomedicinal plant species were documented belonging to 147 genera and 78 families.  Except for three species, the 171 species are Angiosperms mostly collected from the wild.  Among the 174 species of medicinal plants, 12 species are listed under various categories by IUCN and CITES.  All these plants are used to treat various diseases that are grouped under 13 ICPC (International Classification of Primary Care) disease categories, with the highest use value (0.54) recorded in Leucas aspera followed by Paederia scandens with (0.5) use value.  This confirms that these plants are important traditional herbs with potent medicinal uses.  The highest informant consensus factor with the highest number of species (93) being used for the digestive system (FIC= 0.76%), followed by oral and dentistry (FIC= 0.73%) category.  The ethnic communities in the district are rich in traditional knowledge which is evident from the use records and high degree of consensus among the informants.

The floristic composition of the Dibrugarh District of Assam has remained unexplored and the present study on Angiosperms addresses this fact. A total of 462 species of flowering plants belonging to 334 genera under 106 families recorded as per the APG IV system of classification and 116 families were recorded according to Bentham and Hooker system. 39% of native species were included in superorder Superrosids, 29% from superorder Superasterids, 18% from superorder Monocots and 7% from superorder Magnoliids. The orders with the highest number of native species were Lamiales (35), Malpighiales (29), Rosales (26), Gentianales (23), Sapindales (18), Fagales (19), Alismatales (17), Poales (14), Zingiberales (13) and Laurales (11) which accounted for 60.8% of the species. A total of 129 non-native or invasive species were represented in 12 superorders. Habit analysis showed that herbs were represented by the highest proportion followed by trees, shrubs and climbers. Twenty species are listed under various IUCN threat categories and one species under Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Traditional uses of some reported species were also documented. The present study was conducted to understand the diversity of local flora, which can be helpful in the conservation of natural vegetation and sustainable utilisation of resources in this region.