Citronella and lemongrass are not the same thing, though they are closely related botanical cousins. Both are tropical grasses that produce distinct, lemon-scented essential oils, which is the source of common confusion. They are separate species with unique properties determined by their chemical differences. Understanding the science behind these plants reveals why they are used for entirely different purposes, from cooking to pest control.
Botanical Identity and Relationship
Citronella and lemongrass are both members of the genus Cymbopogon, a group of over 70 species of aromatic grasses in the Poaceae family. This shared genus explains their similar appearances and aromatic profiles. However, they belong to different species. Lemongrass is most commonly derived from Cymbopogon citratus or Cymbopogon flexuosus, while citronella comes from Cymbopogon nardus (Ceylon type) or Cymbopogon winterianus (Java type).
The two grasses are native to tropical regions of Asia and are perennial plants that grow in clumps. A subtle physical difference is that citronella grass tends to be taller, sometimes reaching up to six feet, and often has a magenta or reddish tint at the base of its stems. In contrast, the most common culinary lemongrass species, Cymbopogon citratus, is generally shorter and features entirely green stems. This distinction in species dictates the specific chemical compounds they produce, which is where their practical differences originate.
Distinct Chemical Profiles
The primary difference between citronella and lemongrass lies in the chemical composition of their extracted essential oils, which drives their scent and function. Lemongrass oil is characterized by its high concentration of citral, which can account for 70–85% of its volume. Citral is a mixture of two closely related molecules, geranial and neral, and is responsible for the sharp, pure, and intensely lemon-like fragrance. This bright scent makes it highly valued in food and therapeutic applications.
Citronella oil is dominated by different chemical constituents, primarily citronellal and geraniol. Java-type citronella oil contains a high percentage of citronellal, typically between 31–39%, alongside geraniol. These molecules give citronella a strong, slightly woodsy or floral citrus scent that is less refined and sharper than the aroma of lemongrass. The presence of these specific compounds dictates their primary use, particularly citronellal, which is recognized for its insect-repelling qualities.
Divergent Practical Applications
The chemical differences between the two oils directly lead to their separate primary uses. Lemongrass is a staple in cuisine, particularly in South Asian cooking, where the stalks are used fresh to flavor curries, soups, and teas. The oil’s high citral content is recognized as safe for food flavoring and is often used in aromatherapy for its clean, uplifting scent.
Citronella’s application is almost entirely focused on its functional properties, most notably as a natural insect repellent. The strong, distinctive scent provided by its chemical profile effectively masks the odors that attract mosquitoes and other pests, making it a common ingredient in candles, sprays, and lotions. Due to its flavor profile and the higher concentration of certain compounds, citronella is rarely used in food. It is mainly limited to external applications, such as in household cleaners and perfumes.