The aim of the research was to observe the formation and the maturation of seeds inside the spikes of marjoram, and to determine the best harvest period of the seeds, Seed maturation was observed at two locations with three varieties and three harvest times. Germination capacity was tested and the data were statistically analyzed, Results showed that marjoram began to flower consistently and uniformly all over the plant, with a homogeneous maturation of the seeds following the flowering sequence from the bottom to the top of the spikes. The best period for harvest depends on the variety, The seed colour can be characteristic for the variety, and if generally changed during maturation from white to light brown and dark brown. Only white seeds did not germinate. The productivity of the spike and the stage of development of the seed are strongly correlated.