While a plant commonly known as “citronella geranium” exists, true citronella is botanically distinct from any geranium. This widespread confusion stems from shared aromatic qualities, but the plants belong to entirely different botanical families. Understanding this distinction is important for gardeners and consumers alike.
Understanding True Citronella (Cymbopogon)
True citronella comes from grasses belonging to the Cymbopogon genus, primarily Cymbopogon nardus (Ceylon citronella) and Cymbopogon winterianus (Java citronella). These perennial, aromatic grasses are native to tropical regions of Asia. They are tall, clump-forming plants, reaching 5-8 feet (1.5-2.4 meters) in height and spreading 3-5 feet wide.
Their long, thin, bright green leaves emit a distinct citronella-like fragrance when crushed. These grasses are members of the Poaceae family. The primary use of Cymbopogon species is for extracting essential oil through steam distillation of their leaves and stems. This essential oil, rich in compounds like citronellal, citronellol, and geraniol, is highly valued for its insect-repelling properties.
The “Citronella Geranium” Misconception (Pelargonium)
The plant often marketed as “citronella geranium” or “mosquito plant” is not a true citronella and does not belong to the Geranium genus. Instead, it is a scented Pelargonium, typically a cultivar like Pelargonium citrosum or varieties of Pelargonium graveolens. These perennial subshrubs have fragrant leaves that, when disturbed, release a citrus-like scent reminiscent of citronella, due to volatile compounds like citronellol, geraniol, and limonene.
Despite their common names and citrusy fragrance, these Pelargonium plants are not effective as standalone insect repellents when grown in a garden. Research indicates that simply having the plant nearby does not significantly deter mosquitoes; mosquitoes have even been observed landing on these plants. The idea that they are genetically engineered with citronella grass genes has been disproven. While concentrated essential oil from some Pelargonium species does contain insect-repelling compounds, its efficacy as a repellent is generally less potent and shorter-lasting than true citronella oil.
Key Botanical Differences and Takeaway
The fundamental difference between true citronella and the “citronella geranium” lies in their botanical classification and practical efficacy. True citronella (Cymbopogon) is a grass (Poaceae family) whose insect-repelling properties come from its concentrated essential oil, used in products like candles and sprays. In contrast, the “citronella geranium” (Pelargonium) is a subshrub (Geraniaceae family) whose leaves emit a citrusy aroma when touched, but the living plant does not effectively repel insects in a garden setting. Understanding these distinctions clarifies that while both plants have a similar scent, their origins, characteristics, and practical uses as insect repellents are entirely different.