The fragrant scent of citronella is often associated with natural insect control, leading many people to seek out the living plant for their patios and gardens. This tropical herb produces volatile compounds that can temporarily confuse or deter insects like mosquitoes. However, the plant does not work simply by existing; its potential as a repellent depends on proper identification, cultivation, and application. Maximizing effectiveness requires understanding how to maximize oil production and use the harvested material.
Identifying the True Citronella Plant
The plant commonly sold as a “citronella plant” is often the scented geranium, Pelargonium citrosum ‘Van Leenii’. Although its leaves contain citronellal, it is unrelated to the source of commercial citronella oil. The scented geranium has broad, lobed leaves and is ineffective at repelling insects unless actively crushed.
The true source of the widely used essential oil is Citronella Grass, belonging to the Cymbopogon genus (Cymbopogon nardus or Cymbopogon winterianus). This plant is a tall, clumping grass with narrow, upright leaves, similar to lemongrass. Only the Cymbopogon species contain the high concentration of essential oils necessary for effective repellency.
Basic Care and Optimal Growth
For the citronella plant to produce a potent concentration of aromatic oils, it must be grown in conditions that mimic its native tropical habitat. The grass thrives best when exposed to full sunlight, requiring at least six hours of direct sun daily. Adequate light maximizes the volatile oil content within the leaves.
The plant needs a consistently moist environment but requires well-draining soil to prevent root rot. Amending heavy soil with organic matter helps achieve the necessary drainage. Since Cymbopogon species are sensitive to frost, they are best grown in containers in cooler climates so they can be brought indoors for the winter.
Regular watering, especially during dry periods, supports its vigorous growth habit. For the highest yield of essential oil, leaves should be harvested during the peak of the growing season. This is typically 70 to 100 days after the last major cutting. Harvesting involves cutting the stalks near the base, which encourages dense, fresh growth.
Using the Plant for Insect Repellency
Placing a living citronella plant on a patio provides only a minimal repellent effect. The volatile oil compounds are stored within the leaf cells and are not released in sufficient quantities unless the foliage is disturbed. To activate the plant’s insect-repelling properties, you must physically release the oils.
One practical method is to strategically place containers near high-traffic areas and brush against the foliage to release the scent. For direct application, rub freshly crushed leaves onto clothing or exposed skin. The friction breaks the leaf cells, allowing the concentrated oil to evaporate and create a temporary scent barrier against biting insects.
A simple infused water or room spray can be created by steeping crushed leaves in boiling water for several hours. Once cooled and strained, this infusion can be used as a mild, temporary spray for surfaces or skin. Note that the repellent effect dissipates quickly, requiring frequent reapplication.
Safety and Handling Guidelines
When using crushed citronella leaves directly on the skin, perform a small patch test first. The concentrated compounds can cause skin sensitivity, contact dermatitis, or an allergic reaction in some individuals. Avoid applying the crushed material to broken skin or sensitive areas around the eyes and mouth.
For households with pets, caution is advised, as both Cymbopogon and Pelargonium varieties pose risks if ingested. The scented geranium (Pelargonium citrosum) is toxic to dogs and cats, potentially causing gastrointestinal upset, vomiting, and depression. Cats are particularly susceptible to essential oil toxicity because they lack the liver enzymes needed to metabolize certain compounds.