The smart weeds or Knot weeds are one of the major aquatic and marshy land inhabitants belonging to the Family Polygonaceae are primarily found in damp and marshy places. The present study reveals the fact of occurrence of several (14 Nos.) such species along the course of river Kolong which is a major river of the district Nagaon, Assam, India. Though the Knot weeds are considered as weed, yet a number of economic utilization are also found as revealed from the study. Some of the weeds are rare and endangered due to the loss of habitats and extensive use (eg. Polygonum microcephalum).