Weeds associated with rice fields cause severe yield reduction and many other problems. Effective weed management strategy depends on knowledge of weed seed biology. This study aimed to determine basic seed biology information of seven rice field weeds in Sri Lanka. Seeds were collected from at least five individuals from each species. Dormancy classes of seeds were determined using germination and imbibition experiments. Effect of light, dry storage, temperature and salinity on dormancy and germination was studied. Experiments were conducted with three replicates of 25 seeds. Among the tested species, seeds of Eclipta prostrata and Ludwigia peruviana were non-dormant where the non-treated fresh seeds germinated > 60 %. Seeds of Aeschynomene indica and Melochia corchorifolia are physically dormant as only scarified seeds imbibed and germinated. Fimbristylis miliacea, Cyperus pilosus and L. decurrens seeds germinated only on GA3. Thus, they have physiological dormancy. E. prostrata and L. peruviana seeds required light for germination. Five month- dry storage reduced the viability of E. prostrata seeds. In contrast, dry storage increased the sensitivity to the dormancy breaking treatment of A. indica, M. corchorifolia, C. pilosus and L. decurrens seeds and decreased the sensitivity of F. miliacea seeds. Germination of E. prostrata and L. peruviana seeds decreased with decreasing osmotic potential. Although, dormancy and dormancy breaking requirements vary among study species, keeping the rice field dry during the intercropping period could induce the seed germination of most of the above species and could be used as a mechanism to reduce the soil seed bank.