The paper presents the results of the study of the biological features of Orthosiphon aristatus (Blume) Miq. (awned orthosiphon) in open ground conditions on the Southern Coast of the Crimea and in a greenhouse. Features of fl owering, structure of male and female generative structures are revealed. It has been established that when grown in open ground against the background of regular artifi cial irrigation, active growth and development of Orthosiphon aristatus is observed at a minimum air temperature not lower than +15 °C and a soil surface temperature not lower than +10 °C. Mass fl owering falls on the 2nd–3nd decade of August. At this time, the air temperature is +25 °C. On average, the duration of fl owering of one plant is 25–40 days. In the structure of the fl ower of O. aristatus, the phenomenon of hercogamy is observed, which promotes cross-pollination. Sporogenic tissue in microsporangium is represented by one, very rarely two, rows of large cells with a clearly defi ned nucleus and nucleolus. Pollen grains are 3-celled, most of them are sterile. The ovule of O. aristatus is anatropic, unitegmal and media-nucellar, the vascular bundle reaches chalase and the integumental tapetum is clearly expressed. The maturation of male and female gametes does not coincide in time, protandry is observed. The end of fl owering of O. aristatus falls at the end of September – the beginning of October. In September, in protected ground conditions, slight seed formation is possible.