The increased demand helped create an industry of patchouli farming and distillation in tropical Asia that persists to the present. Patchouli is usually grown on small forest plots by individual farmers who harvest and dry the leaves, then sell them to distilleries throughout the growing region. The still operators buy many lots of dried leaves and combine them into one steam distillation, the results of which may then be combined with successive distillations until they've obtained sufficient quantities of oil. Newly distilled patchouli oil has a fresh, green, slightly harsh aroma. As the oil ages it mellows considerably, becoming sweeter and more balsamic.
Patchouli is one of very few oils that, like fine wine, improve with age.
High quality patchouli oils emit a suave, fruity, wine-like top note when uncapped. Other oils that age well are sandalwood and vetiver, both of which blend quite nicely with patchouli. Adulteration of patchouli is less common than with other essential oils. Heavy cedarwood or spicy clove-like notes may indicate that patchouli oil has been tampered with, usually as a result of a bad crop year or when demand outweighs supply. Patchouli is most often used in aromatherapy.