Floristic survey of weeds with emphasis on organic and conventional tea gardens in South bank of Assam, India

Abstract This study identifies weed species and assesses their frequency, abundance, dominance, and similarity index in selected tea estates on the South bank of Assam. A phytosociological survey of weeds using random quadrat technique of (1x1) m was carried out in tea gardens from 2022 to 2024 at regular intervals to compare the weed flora in organic and conventional tea gardens and identify the most prevalent weeds in the gardens of South Bank of Assam. The floristic diversity of weeds was evaluated for the most dominant weeds based on a higher value of important value index (IVI). 188 different weeds were collected that belonged to 41 dicot families, 6 monocot families, and 7 pteridophytic families which were predominantly therophytes. Native weed species accounted for 71% while exotic species represented 29% of total weeds. Asteraceae (11.53%) and Poaceae (10%) represented the highest number of species. Cluster analysis of weed flora highlighted the species like Ageratum houstonianum, Ageratum conyzoides, Spermacoce alata, Axonopus compressus and Oxalis debilis to be higher in organic gardens. Herbicide resistant weeds like Polytrias indica, Eleusine indica, Paspalum conjugatum, Oplismenus compositus and Cyperus brevifolius have shown higher frequency, density and abundance than other weeds in conventional gardens. The study also found the presence of Ageratum conyzoides, Spermacoce alata, Eleusine indica, Mikania micrantha, Peperomia pellucida, Chrysopogon acicularis, Clerodendrum infortunatum, Colocasia esculenta and Crassocephalum crepidiodes in all selected gardens regardless of cultural practices.