As a useful tool to elucidate gene functions, a rice transposon tagging line has been developed using an active endogenous DNA transposon, nDart1. It was highly desirable to evaluate the transposition timing and frequency of the nDart1 elements during rice development to facilitate the generation of an efficient mutant isolation system. Comparison of the detected new insertions at different stages of rice development by transposon display analysis demonstrated that the last heading tiller carry a higher number of nDart1 elements than the main culm. Moreover, it was revealed that the last heading tiller could produce progeny that carried more new insertions of nDart1 elements, mainly as a result of the accumulation of somatic insertions in the parental plant. This report demonstrates that late tillers increase the probability of producing independent mutant lines.