Analysis of Morphological Traits, Essential Oil Yield, and Secondary Metabolites in Seven Lavandins and Lavenders Grown in Two Pedoclimatic Areas in Tuscany (Italy)

Plants of the genus Lavandula are widely studied for their pharmaceutical and food relevance. The composition of lavender essential oil is primarily genotype-dependent but also influenced by environment, developmental stage, and morphology. This study assessed biomass, morphology, oil yield, and chemical composition of seven cultivars (L. angustifolia Boston Blue, L. angustifolia Dwarf Blue, L. Abrialis, L. Super A, L. Super Z, L. Maime, and L. sumiens) cultivated in Tuscany (Italy) over two growing seasons years (2019–2020 and 2020–2021) at two sites (IT and VR). Most morphological traits were significantly affected by cultivar, site, and year, with IT and lavandin cultivars outperforming VR and true lavender. Cultivar strongly influenced compound concentrations, confirming genetic control. True lavender oils showed distinctive profiles compared to ISO 3515:2002/Cor 1:2004 and the literature: lower linalool (~12.8% vs. 25–38%), higher linalyl acetate (~22.7% vs. 25–45%), negligible camphor (~0%), and very low 1,8-cineole (0.7%). Lavandin oils matched ISO 8902:2009 and the literature for major compounds (1,8-cineole 7%, camphor 8.9%, and linalool 23.4%), except for linalyl acetate (14.2%), below the standard range (20–38%). Overall, cultivar choice significantly shaped essential oil yield and chemical profiles, highlighting genetic and environmental interactions that are crucial for lavender breeding and industrial applications.