The citronella plant is widely recognized for its association with mosquito repellency, making it a popular choice for gardens and outdoor spaces. The term “citronella plant” commonly refers to two distinct botanical types: the true citronella grass (Cymbopogon nardus or Cymbopogon winterianus) and the citronella scented geranium (Pelargonium citrosum).
Identifying Citronella Plants
The true citronella plant is a perennial clumping grass (Cymbopogon nardus or Cymbopogon winterianus). It can grow quite tall, reaching heights of 4 to 6 feet and widths of 4 feet. These grasses feature long, slender, medium-green blades, often with reddish bases, forming dense clumps.
The plant often marketed as a “citronella plant” or “mosquito plant” is typically a citronella scented geranium (Pelargonium citrosum). This subshrub has lacy, scalloped, green foliage that emits a citrusy scent when touched or crushed. It also produces small pink, purple, or white flowers, especially from spring through fall. While both are associated with the citronella scent, their growth habits and appearance differ significantly.
Growing and Caring for Citronella
Successful cultivation of citronella plants involves understanding their specific environmental preferences. Providing the right conditions helps ensure a healthy and vigorous plant.
Light and Location
Citronella plants thrive in full sun to partial shade, ideally receiving at least six hours of sunlight daily. In regions with intense summer heat, providing some afternoon shade can prevent leaf burn. For indoor cultivation, placing the plant in a sunny window, such as a south or west-facing exposure, is beneficial. Insufficient light can cause the plant to become tall and leggy.
Soil and Watering
Well-draining soil is important for citronella plants, as they are susceptible to root rot. A sandy loam rich in organic materials, with a slightly acidic pH between 5.8 and 6.3, is ideal. Allow the top inch or two of soil to dry out completely before watering again. While they can tolerate some drought, consistent moisture is preferred, especially for potted plants.
Temperature, Humidity, and Fertilizing
Citronella plants prefer warm temperatures, ideally between 50°F and 80°F (10°C and 27°C), and are sensitive to frost. They are perennials in USDA hardiness zones 9 to 11, but are often grown as annuals or overwintered indoors in cooler climates. Moderate to high humidity levels, around 40% to 70%, are beneficial. Young or potted plants benefit from a balanced, water-soluble fertilizer applied every two to four weeks at half strength.
Pruning and Propagation
Regular pruning helps maintain a bushy and compact shape, preventing leggy growth. Pinching back growing tips encourages branching and more blooms. Remove dead or yellowing leaves to maintain plant health. Citronella plants can be propagated through 3-6 inch stem cuttings with several leaf nodes. Cuttings can be rooted in water or directly in moist, well-draining soil, sometimes with rooting hormone. Division is also an effective propagation method for clumping varieties.
Citronella’s Mosquito Repellent Qualities
The mosquito-repelling properties of citronella plants stem from essential oils in their foliage, particularly compounds like citronellal, citronellol, and geraniol. These compounds mask scents that attract mosquitoes, interfering with their ability to locate hosts. While concentrated citronella oil in products like candles or sprays can be effective, the plant itself offers a more limited repellent effect.
To release the full scent from the plant’s leaves, physical interaction, such as crushing or brushing against them, is necessary. Simply having the plant nearby may not provide substantial mosquito protection. For practical use, strategically place plants in high-traffic outdoor areas, like patios or near entryways, to maximize the release of their aromatic compounds when disturbed.
Troubleshooting and Safety
Yellowing leaves often indicate overwatering, underwatering, or insufficient light. Overwatering can lead to root rot, so allowing the soil to dry out between waterings is important. If the plant appears leggy, it likely needs more sunlight. Common pests like spider mites and aphids can occasionally affect citronella plants, causing yellowing, dropping, or curled leaves. These pests can often be managed with strong water sprays or insecticidal soap.
Pelargonium citrosum, the scented geranium, can be toxic to pets, particularly cats and dogs, if ingested. The plant’s essential oils can also cause skin irritation in some individuals upon direct contact with the sap. Handle the plant with care, especially when pruning or crushing leaves, and keep it away from pets.