Information on the influence of temperature on growth of spring Triticum aestivum L. (wheat) relative to Kochia scoparia (L.) Schrad. (kochia) and Salsola iberica Sennen and Pau (Russian thistle) could lead to more efficient weed management practices. An experiment was conducted to determine the growth of spring T. aestivum, K. scoparia, and S. iberica at 15, 23, and 30 C in growth chambers. Fresh weight at 15 C was greater for spring T. aestivum than for K. scoparia and S. iberica. Conversely, fresh weights at 23 or 30 C were greater for K. scoparia and S. iberica than for spring T. aestivum. Growth response to temperature is consistent with the physiological characteristics for photosynthesis of spring T. aestivum, a C3 plant, and K. scoparia and S. iberica, which are C4 plants. The results indicate that cool temperatures that usually occur for early-seeded spring T. aestivum would give spring T. aestivum the competitive advantage over K. scoparia or S. iberica. Additionally, growing degree day (GDD) equations for height development of K. scoparia and S. iberica were determined and could be used to determine the optimum time for postemergence herbicide application.