Lemongrass, or Cymbopogon citratus, is a highly aromatic herb popular in gardens due to its pleasant, citrus-like scent. This strong fragrance has led to the belief that planting the herb creates a natural, mosquito-free zone. The plant’s reputation for deterring insects is well-founded, as its volatile oils contain protective compounds. However, the core question is whether the intact, living plant itself is sufficient to keep biting insects away.
The Distinction Between Lemongrass and Citronella
Confusion regarding lemongrass’s effectiveness often stems from its close botanical relationship with citronella grass. Both belong to the Cymbopogon genus, but the primary repellent power comes from two different species: West Indian lemongrass (C. citratus) and citronella grass (C. nardus or C. winterianus). Lemongrass oil contains high concentrations of citral, which provides its distinct lemon aroma.
Citronella oil, an ingredient in many commercial repellents, is extracted from the leaves and stems of citronella grass. This oil is rich in citronellal and geraniol, the main chemical components responsible for insect deterrence. While lemongrass does contain small amounts of these protective compounds, the concentrations are highest in the essential oil derived from citronella grass. This difference in chemical composition means citronella oil is traditionally considered the more potent natural option for protection.
Effectiveness of the Living Plant
Despite its strong smell, a living lemongrass plant provides limited protection from mosquitoes in a garden setting. The insect-deterring compounds are stored within the plant’s cellular structure and are not readily released into the surrounding air. The leaves are not sufficiently volatile to create a protective cloud or barrier that would shield a person sitting nearby.
Scientific studies confirm that the living plant is considerably less effective at repelling mosquitoes compared to its extracted essential oil. A single potted plant cannot produce the high concentration of airborne molecules necessary to interfere with a mosquito’s ability to locate a host. For the plant to release a meaningful amount of the active compounds, the leaves must be physically crushed or bruised, which breaks the cellular walls and allows the volatile oils to escape. Relying on intact plants to guard an entire outdoor area is largely ineffective.
Mechanism of Citronella Repellency
The oils derived from citronella and lemongrass do not repel mosquitoes by driving them away, but rather by disrupting their sensory systems. Mosquitoes are primarily attracted to humans by the carbon dioxide we exhale and the lactic acid present on our skin. These attractants are detected by specialized receptors on the insect’s antennae.
The volatile compounds in the essential oils, such as citronellal and geraniol, temporarily mask these host-seeking scents. By overloading the mosquito’s odor receptors, the compounds make it difficult for the insect to accurately locate a target. This interference creates a “smoke screen” that prevents the mosquito from registering the presence of a person.
Utilizing Lemongrass Extracts for Protection
To gain effective protection from lemongrass compounds, the essential oil must be extracted and applied topically or diffused. The most successful method involves diluting the essential oil with a carrier oil, such as coconut or jojoba oil, before applying it directly to exposed skin. Undiluted essential oils can cause skin irritation, so proper dilution is necessary to ensure safety.
Research shows that diluted lemongrass essential oil can provide significant protection, sometimes up to 98% for a limited period. However, the volatile nature of the oil means it evaporates quickly, requiring frequent reapplication, often every 30 to 60 minutes, to maintain effectiveness. Rubbing freshly crushed lemongrass leaves directly onto the skin will release the protective compounds, although this method should be used cautiously due to potential skin sensitivity.