Phenotypic and Phytochemical Variability Among Four Populations of Hedeoma multiflora Benth. (Tomillito de las Sierras) Native to the Province of Córdoba—In Situ Evaluation

Hedeoma multiflora Benth. is an endangered aromatic and medicinal wild species native to Argentina, widely used in traditional medicine, whose cultivation represents a small and untapped sector within the agricultural industry. Current market supply relies on wild harvesting practices by rural communities, leading to population decline and genetic diversity loss through inappropriate extraction methods, including uprooting during suboptimal phenological stages. This study evaluated phenotypic and phytochemical variability in four populations of H. multiflora in the province of Córdoba to develop conservation strategies and cultivation protocols. Forty individuals were sampled from each population to analyze morphological, chemical, phenological, edaphological, and climatic variables. Significant differences were observed between populations: Tulumba had the tallest plants and largest leaves, while Bialet Massé had the highest number of internodes. Essential oil yield ranged from 1.01% to 2.10%, with Ongamira having the highest content. Phytochemical analysis revealed two chemotypes: pulegone-dominant (Bialet Massé and Río Cuarto) and menthone-dominant (Ongamira and Tulumba). Phenological patterns differed significantly, with Ongamira showing the greatest reproductive synchronization. Soil organic matter content significantly influenced morphological and chemical traits. The high variability among populations underscores the importance of preserving genetic diversity for domestication and conservation strategies.