The influence of three aromatic plant species, laurel (Laurus nobilis L.), myrtle (Myrtus communis L.), and French lavender (Lavandula stoechas L.), on top soil microbial biomass, respiration rates, and bacterial colonies was investigated. Fresh, mature plant material was introduced into a typical Mediterranean habitat in Northern Greece. The essential oil chemical compositions from the aromatics used in the study were evaluated by GC-MS analysis. The major compounds constituting L. nobilis essential oil were 1,8-cineole (48.1%), eugenol (12.3%), and α-pinene (6.0%); M. communis oil consisted of α-pinene (31.2%), myrtenyl acetate (19.3%), and 1,8-cineole (16.1%); and L. stoechas consisted of fenchone (46.7%), camphor (9.9%), and 1,8-cineole (9.0%). L. nobilis presented the highest inhibition against bacterial colonies (44.9%) and lowered soil respiration and microbial biomass when compared to control soils. In contrast, M. comunnis and L. stoechas were found to augment bacterial activity by 85.9% and 63.8%, respectively, and to increase soil respiration (1.5-fold) and microbial biomass (2.5-fold) compared to control soil samples. These two plants are proposed for further investigations in biodegradation programs.