An experiment aimed at studying the flowering dynamics and seed production of Desmodium incanum DC. in the conditions of the Depressão Central region was conducted in the Agronomic Experimental Station of the Universidade Federal do Rio Grande do Sul, in Eldorado do Sul, RS, from october 1995 to april 1996. The experimental design was of randomized blocks with three replicates. Samples of 0.25m2 were weekly collected to determine total number of inflorescences/m2 , number of floral nodes/inflorescence, number of floral organs/inflorescence, number of articules/loment, number of seeds/loment, seed weight and potential and estimated seed yield/area. D. incanum had a long flowering period, from october to april. The best time for seed harvest was around 2000 degree days, calculated from plant growth restarting. Maximun estimated seed yield (361kg/ha) was much lower than potential yield (7335kg/ha). Number of mature loments per inflorescence was the most limiting component of seed yield, probably due to the high flower abortion rate and lack loment maturation in the inflorescences.