The citronella plant, with its distinctive citrusy fragrance and often lacy, green foliage, is a popular addition to many gardens and patios. Cultivated in containers or garden beds, its bushy growth (typically two to three feet tall and wide) makes it both a decorative element and an aromatic plant.
The Main Benefit: Mosquito Deterrence
The citronella plant’s main appeal is its perceived ability to deter mosquitoes. This deterrence comes from aromatic compounds like citronellol and geraniol within its leaves. When disturbed (by brushing or crushing), these volatile oils release a lemony scent. This scent is thought to mask human odors, making it harder for them to locate their targets.
However, the plant’s effectiveness as a standalone mosquito repellent is overstated. While it contains repellent compounds, it doesn’t continuously emit enough oils to create a wide protective barrier. For a noticeable effect, leaves generally need to be physically crushed or rubbed to release a higher concentration of aromatic oils.
Studies show the plant alone provides limited protection compared to essential oils or synthetic repellents. Citronella essential oil, especially when formulated correctly, shows more significant repellent activity, sometimes comparable to DEET for a limited duration. Citronella products typically offer shorter protection compared to DEET.
Understanding Citronella Plants
A common source of confusion arises from the term “citronella plant,” as it can refer to different species. True citronella grass, the primary source of commercial citronella essential oil, belongs to the Cymbopogon genus (Cymbopogon nardus or Cymbopogon winterianus). These tall, perennial grasses, native to Asia, have long, thin leaves and a strong lemon scent. Their essential oil contains a high concentration of insect-repelling compounds.
Conversely, the “citronella plant” or “mosquito plant” commonly sold in nurseries is a scented geranium, Pelargonium citrosum. While this Pelargonium emits a citrusy scent when its lacy leaves are touched, its concentration of repellent compounds is not high enough to deter mosquitoes effectively. Despite its pleasant fragrance, studies show Pelargonium citrosum provides little significant mosquito repellency on its own. This distinction is important, as efficacy depends on the essential oil from Cymbopogon grasses or the scented geranium plant.
Cultivating and Utilizing Your Plant
Cultivating citronella plants involves straightforward care for their aromatic properties. Both types thrive in ample sunlight (at least six hours daily), though they can benefit from afternoon shade in hot climates. They prefer well-drained soil; enriching it with compost promotes healthier growth. Water when the top inch or two of soil feels dry; avoid overwatering to prevent root rot.
Citronella plants are sensitive to cold and cannot tolerate frost, typically grown as annuals in cooler climates. In USDA Hardiness Zones 9 to 11, they can be grown as perennials. For optimal aromatic benefits, strategic placement is helpful, such as near seating areas, doorways, or walkways, encouraging scent release when brushed. Gently crushing the leaves also intensifies the release of their oils. Beyond any repellent qualities, these plants add ornamental value and a pleasant citrus aroma to outdoor spaces.