A plant activator composition increases the concentration of terpenes and terpinoids in aromatic plant oils, and hence resulting in an increased concentration of terpene and terpinoids in the harvested dried plant or fruit. The composition contains one of more bio-active compounds that are optionally extracted from plants selected from one or more of the group consisting of mango, citrus (including grapefruit), Catharanthus roseus and Pelargonium odoratissimum, but alternatively may include one or more synthetic compounds selected from the group consisting of geranyl acetate, geraniol, beta-sitosterol, alpha-amyrin, beta amyrin, carotenoid, geranyl acetate, alpha-humulene, mevalonate kinase and geranyl. Depending on the type of plant being treated, the formulation is added during watering and feeding in optimum doses during the vegetative growth, flowering, and fruit set and/or swell stages.
