Promotional literature claims that citrosa has been genetically engineered to produce citronella oil, but chemical analysis has shown that citrosa essential oil contains only trace amounts of citronella (11 percent citronellol, 0.09 percent citronellal), and, in fact, closely resembles the essential oils of the other geranium plants.(*) The citrosa plant is morphologically similar to the cultivar Pelargonium "Rosé" (P graveolens L'Hérit. x Ait., Geraniaceae or rose geranium), which is part of the hybrid complex P x asperum Ehrh. ex Willd. = P graveolens L'Hérit. x P radens H. E. Moore. In fact, the citrosa plant is essentially indistinguishable from the P xasperum hybrid complex. Despite the marketing, "Pelargonium citrosum" is not a valid taxonomic designation. Based on the results of this study, the authors conclude that citrosa should not be marketed as a mosquito repellent.
[Matsuda, B. M., G. A. Surgeoner, J. D. Heal, A. O. Tucker, and M. J. Maciarello. 1996. Essential Oil Analysis and Field Evaluation of the Citrosa Plant "Pelargonium citrosum" as a Repellent Against Populations of Aedes Mosquitoes. Journal of the American Mosquito Control Association, Vol. 12, No. 1, 69-74.]
((*) Oil of Ceylon citronella grass (Cymbopobon nardus) has an average of 14 percent citronellal and 12 percent citronellol. The oil of java citronella grass (C. winterianus) has, on average 2 percent citronellal and 16 percent citronellol. -- Lecture by Tucker, A. and M.J. Maciarello, Is This Plant a Hoax?)
Article copyright American Botanical Council.
By Ginger Webb