The quantity of essence synthesized in the extraordinary laboratory of plants is not always the same during the course of the year, on the contrary it varies greatly. The aromatic principles appear in the green parts of the plant starting from the first months of life and continue to form and accumulate until the beginning of flowering. As flowering progresses, the plant slows down the process of formation of these substances which pass, by diffusion, from the leaves to the stems and from the stems to the flowers or fruits, where they are enclosed in particular micro-pockets. Here they are partially consumed during fertilization, after which they return to the stems and other green organs.
Throughout the life cycle of the plant, therefore, the essences continuously change their chemical composition and move from one part to another according to the time of day, the season or needs.
The moment in which the plant is richest in essential oils is called the "balsamic moment". The plants intended for the extraction of the essential oil, therefore, must be harvested in a certain period of the year and in certain hours and weather conditions to obtain a better qualitative and quantitative yield. In some plants, curiously, the balsamic moment is linked to the day-night cycle: jasmine must be picked before sunrise, Gladiolus tristis is perfumed only at night. Then there are aromatic herbs such as valerian which produce aromas only during drying.
