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Citronella Plants - Do They Really Work?
Do plants with a citronella-like scent really repel mosquitoes? Geraniums with such a scent have been marketed as effective mosquito deterrents.
Researchers at the University of Guelph in Ontario, Canada tested citronella-scented geraniums for their mosquito repelling power. The study examined the repellent properties of a plant marketed as Pelargonium citrosum 'Van Leenii'. The Journal of the American Mosquito Association (vol.12,no.1), reports detailed testing with human volunteers found no significant difference in the number of bites received by those who stood with plants versus those who stood "plantless" in a mosquito infested area.
Laboratory analysis of the chemical makeup of P.'Van Leenii' revealed only trace amounts of citronellol, the main compound in citronella oils. Researchers concluded that P.'Van Leenii' was barely distinguishable from the rose-scented geranium, a favorite in potpourri mixes and jellies.
So, unfortunately, citronella-scented plants will probably not give you satisfactory protection from mosquitoes. (Source:Horticulture magazine, July/August 1998)