The study examined the effect of the pod colors as an index of maturity phases on seed traits of silk tree (Albizia julibrissin Durazz). Silk tree pods were simultaneously collected at five maturity phases based on pods color in late September in the Hyrcanian plain forest, Tashbandan-Iran. Seeds were removed from pods and seed moisture content (MC), 1000 seed weight (1000 SW) and germination performance were determined. Maturity phases affected seed MC and 1000 SW. MC and 1000 SW were the highest at the pod color of full green (61% and 64.2 g, respectively). As the seeds matured, MC and 1000 SW decreased, and the lowest MC and 1000 SW were found as 8.5% and 36.2 g, respectively at seeds harvested at the dark brown stage. Germination percentage (GP), germination speed (GS) and mean germination time (MGT) were significantly affected by seed maturity phases, and GP and GS were the lowest in the dark brown pod stage (6% and 0.2, respectively). GP and GS was the highest at seeds harvested at the half green-half brown stage. MGT was increased to the maximum when seeds were harvested at the dark brown pod stage (29.8). This study showed that when pods have reached maturity, the coats of the seeds have no barrier to germination but as ripening continues, germination of silk seeds were hindered by impervious seed coats that retard the entry of water. The study revealed that pod color could be used as an indicator for physical dormancy level of silk tree seeds.