Crop diversity could foster low weed density but high weed diversity. Weed and management data was collected from organic spring cereals fields in 5 different regions in Northern Europe. The effect of crop diversity strategies on weed density, diversity, community and traits was studied. Results show that direct weed control lowers weed densities, but long term strategies such as winter catch crop use and organic management increase weed diversity, without increasing densities. When looking into trait selection, only a few traits were influenced by crop management and diversity.