Common waterplantain (Alisma triviale) interference with wild rice (Zizania palustris).

Three cvs. of wild rice (Zizania palustris) were grown with various densities of Alisma triviale established either from seeds or rootstocks in 1979 and '80. Wild rice cvs. did not differ in their response to A. triviale. A. triviale grown from seed at densities up to 82 plants/m2 did not significantly reduce the yield of wild rice. However, A. triviale grown from rootstocks reduced wild rice yields at densities as low as 3 plants/m2 while 43 plants/m2 reduced the yield 91%. The number of panicles/plant was the yield component most susceptible to competition from A. triviale. The stand of wild rice was reduced by A. triviale only at a density of 43 plants/m2. A. triviale established from rootstocks at a density of 17 plants/m2 did not reduce wild rice yield provided that the weed was removed within 7 weeks of sowing. Competition with A. triviale for 9 weeks or more at this density reduced wild rice yield approximately 50%. From summary.