Weedy rice is causing problems for California rice farmers by competing with cultivated rice, leading to lower yields and quality. A study looked at how a popular rice variety, M-206, responded to competition from different weedy rice types. M-206 initially grew faster when competing with weedy rice, but its growth slowed down as it matured. The presence of weedy rice reduced M-206's plant height and tiller number, resulting in significant yield losses at high weed densities. Weedy rice biotypes varied in their growth rates and yield, with most producing taller plants and higher grain yields than M-206 under competitive conditions.