The present invention relates to a method of controlling weeds in a crop fields, land under perennial crops, or a non-crop land, the method comprising applying an effective amount of crystal of flumioxazin which shows a powder X-Ray diffraction pattern having diffraction peaks with 2θ values (°) shown in Table 1, said pattern being obtained by CuKα rays diffraction analysis,TABLE 12θ value (°) 9.8 ± 0.111.4 ± 0.112.7 ± 0.113.8 ± 0.116.0 ± 0.116.4 ± 0.116.7 ± 0.1to soil where the weeds are grown or to be grown, or weeds.According to the present invention, a wide range of weeds can be controlled in a crop field, land under perennial crops, or a non-crop land.
