Corn mint (Mentha arvensis, Lamiaceae), common in the middle-latitude climatic regions of Eurasia,is both a weed and a medicinal plant, the essential oil of which is included in the European Pharmacopoeia (European Pharmacopoeia, 2024). Plants of this species can intensively spread vegetatively as a weed with their creeping, abundant branched rhizomes and influence the growth and development of neighbouring plants through the allelopathically active biochemical compounds released from the underground parts into the soil. Due to gynodioecy characteristic of generative reproduction and intensive interspecific crossing, corn mint is characterized not only by a large interspecific diversity of morphological and anatomical features, but also by chemical polymorphism. Corn mint is the main source of natural origin menthol, widely used in food, pharmaceutical and other industries. This compound can make up to 80% of the essential oil of corn mint, but according to exploratory and unpublished research data, menthol has not been detected in plants of this species growing wild in Lithuania. Polymorphism is significantly influenced by the environment in which the plant grows. Therefore, the aim of the work should be to investigate the relationship between the corn mint polymorphism and environmental conditions, determining which chemotypes of corn mint are common in Lithuania and how this distribution depends on the environment. The allelopathic properties of different chemotypes of corn mint will also aim to determine.