Putievsky, E., Department of Medicinal Spice and Aromatic Plants, Agricultural Research Organization, Experiment Station Post, Haifa, 31-999, Israel
Ravid, U., Department of Medicinal Spice and Aromatic Plants, Agricultural Research Organization, Experiment Station Post, Haifa, 31-999, Israel
Dudai, N., Department of Medicinal Spice and Aromatic Plants, Agricultural Research Organization, Experiment Station Post, Haifa, 31-999, Israel

By harvesting at different dates and frequencies, we have shown the influence of flowering on the essential oil of a clone of oregano grown under cultivation. Flowering increased the essential oil content. In non‐flowering plants the highest level of essential oil was obtained in June. The proportion of thymol and γ‐terpinene (1‐methy1–4‐(1‐methylethyl)‐1,4‐cyclohexadiene) in the essential oil varied during different months in non‐flowering plants as well as in different stages of flowering at the same date of harvest. Increase in the content of one of the two components was accompanied by decrease in the other one and vice versa. Flowering and season had no influence on the content of the other two main components in the essential oil (p‐cymene and carvacrol). Copyright © 1988 John Wiley & Sons, Ltd