Citronella plants are actually a type of scented geranium. The citronella oil we know is an essential oil produced by the leaves and stems of lemongrass plants of the Cymbopogon genus. Citronella and lemongrass are two different plants that both contain citronella. The citronella in these plants masks the scents mosquitoes usually rely on to target their hosts. The citronella plant has a reddish stem, while lemongrass consists of a uniform green stem.