Common Waterplantain (Alisma triviale) Interference with Wild Rice (Zizania palustris)

Three cultivars of wild rice (Zizania palustrisL.) were grown with various densities of common waterplantain (Alisma trivialePursh) established from seeds and from rootstocks during 1979 and 1980. Wild rice cultivars did not differ in their response to common waterplantain interference. Common waterplantain grown from seeds at densities up to 82/m2did not significantly reduce wild rice yield. Common waterplantain established from rootstocks significantly reduced wild rice yield at densities as low as 3/m2. A density of 43/m2reduced wild rice yield by 91%. The yield component most susceptible to interference from common waterplantain was panicles per plant. The number of seeds per panicle was reduced by densities as low as 11/m2and seed weight was reduced by densities of 22/m2or greater. Only a density of 43/m2reduced the stand of wild rice. Common waterplantain established from rootstocks at a density of 17 plants/m2did not reduce wild rice yield if removed by 7 weeks after planting. Interference from common waterplantain for 9 weeks or longer reduced wild rice yield by approximately 50%.