Geographical and seasonal variation studies (important for
potential commercialization) have been undertaken on the essential
oils of selected aromatic plants. The chemical composition has
been reported together with the antimicrobial activity in order to
give some indication as to how the climatic or geographical factors
may influence the phytochemicals and their resultant biological
activity. These include the quantitative and qualitative variation of
Artemisia afra (Viljoen et al., 2006a), Lippia javanica (Viljoen et al.,
2005) and Mentha longifolia subsp. polyadena (Viljoen et al., 2006b).