This article presents data on the species diversity of Juncaceae and the Poaceae families, widespread in the natural lowland ecosystems of Karabakh. An attempt has been made to enlighten their phytocenological features and ethnobotanical characteristics as reflected in their use among the population. Based on the geobotanical studies carried out, the current state and taxonomic composition of natural phytocenoses was established. The species distribution was recorded, herbarium specimens collected, analyzed and identified. The composition and structure of phytocoenoses and taxonomic status of genera and species was pooled up. In the light of findings collected from the literarature and research conducted in the lowland regions of Karabakh, it was established that family Poaceae Barnhart is represented by 108 species belonging to 55 genera, and family Juncaceae includes 12 species belonging to two genera. On the basis of ethnobotanical surveys, information was obtained about a number of useful plants used by the population. Juncus species are mainly used as fodder plant and in basket weaving. Whole aerial parts of J. articulatus are used for diseases of the gastrointestinal tract, liver disorders and as a choleretic and expectorant, as well as for skin diseases, tumors, and promoting the healing of purulent wounds. The species present in the study area are also utilized as food, in animal husbandry, agriculture, and as building materials. Analysis across 18 different age groups revealed that many medicinally significant grass species common in the area remain unused.