Abstract Weed seed buoyancy and survival in irrigation ponds were investigated as part of a larger study evaluating the potential for weed seed spread via overhead irrigation in container nurseries. Seed buoyancy was assessed for thirteen weed species common to container nurseries. Two of the thirteen species were tested with the pappus intact or removed. Seeds were placed in water, and seed settling was recorded every 24 h for 168 h. Among the species tested, seed buoyancy ranged from 0% to 100%. Eclipta and marsh yellowcress maintained 100% and 99% buoyancy. In contrast, flexuous bittercress and yellow woodsorrel had 2% and 0% buoyancy. An attached pappus significantly increased seed buoyancy for both common groundsel and dogfennel. To test seed survival in irrigation ponds, seeds of spotted spurge, eclipta, flexuous bittercress, and yellow woodsorrel were placed in mesh bags and submerged at a depth of 60 cm in irrigation ponds at four nurseries. Seeds were collected from each location at 7, 15, 21, 30, 60, 90, 120, 240, and 360 days after submergence then germinated. All weed species germinated following 240 days of submergence. Flexuous bittercress and eclipta maintained over 80% germination following 360 days of submergence in three of four locations. In contrast, yellow woodsorrel seed germination was less than 15% following 240 days of submergence and less than 5% after 360 days in three of four locations. Spotted spurge seed germination declined over time but remained greater than 15% following 360 days of submergence. Results of these experiments show that seeds of several common nursery weeds are buoyant and remain viable while submerged for extended periods of time in irrigation ponds. Seeds that are both buoyant and survive in water may have greater potential for distribution by irrigation systems.
Ray et al. (Thu,) studied this question.