Rice is the grain with the third-highest global production. In the US, Arkansas is the largest rice producing state; however, an estimated 62% of the rice fields in the state are infested with red rice, and can cause up to 80% yield reduction in rice. Among its weedy traits, seed dormancy plays an important role in its persistence, and helps red rice escape weed management techniques thereby increasing the red rice soil seedbank. Red rice also has the potential to hybridize among themselves and with cultivated rice, thus resulting in diverse phenotypes and genotypes. In this study we measured variation in seed dormancy at different after-ripening times, and incubation temperatures; determined the genetic diversity of dormant and non-dormant red rice populations; measured diversity in phenological and morphological traits among and within red rice populations collected across Arkansas; and, determined the genotype-phenotype relationship and population structure of old and recent red rice collections using sequence tagged site (STS) markers.