Introduction: Common oregano is an important medicinal and aromatic plant, characterized by a high morphological and chemical variability.
Objective: The aim of the work was to determine the diversity of 14 common oregano populations introduced into ex situ conditions, in respect of morphological and developmental traits as well as content and composition of essential oil in herb.
Methods: Observations and harvest of raw material were performed in the second year of plant vegetation. Morphological and developmental characters were estimated. Total content of essential oil was determined according to European Pharmacopoeia 8th. The composition of essential oil was carried out by gas chromatography.
Results: Populations differed in respect of examined traits, i.a.: plant's height from 52.13 to 88.66 cm, number of stems per plant from 45.6 to 123.3, number of internodes per stem from 4.6 to 9.2. Fresh mass of herb was at a level of 249.0–896.6 g per plant. Total content of essential oil ranged from 0.35 to 0.87%. Sabinene, 1,8-cineole, linalool, p-cymene, β-caryophyllene and caryophyllene oxide were the dominant compounds in essential oil.
Conclusions: Number of stems and fresh mass of herb differentiated examined populations at the highest degree. Most of populations were classified as a sabinyl chemotype rich in sesquiterpenes.