Each species and cultivar in the Lavandula genus runs its own genetic program and biosynthesis machinery, rendering its own “unique formula” for its essential oil. Additionally, cultivation and seasonal weather conditions can also affect production of the hundreds of component oil molecules. Since the constituent compounds in the oils each have unique aromas, the composite fragrances tend to be distinct in side-by-side comparisons. Attempts are often made to alter the natural oils in order to obtain a more consistent batch-to-batch fragrance (such as “40/42 standardization” of two of the main components of lavender essential oil). But for unaltered oils, it is perhaps best simply to understand the basis for the variability, and appreciate the differences resulting from the natural processes they represent.