This book comprises an introduction, study species, materials and methods, flora and vegetation, weed-crop interaction of two common cereal crops (wheat and maize) in Egypt. In addition to a general discussion and list of references. The book deals with the study of the floristic and vegetation analyses of wheat and maize crops and their associated weeds and the environmental variables affect them. It also evaluates the weed-crop interaction, in terms of density and biomass, and its impact on the crop yield, in addition to the impact of nutrients and trace metals capture by weeds on the nutrient absorption and production of the study crops. Moreover, the impact of weeds on the functional traits of wheat and maize plants was also investigated.