Citronella is a genus of flowering trees and shrubs in the family Cardiopteridaceae within the order Aquifoliales. The genus was first described by the Scottish botanist David Don in 1832 and comprises approximately 20 accepted species distributed across tropical regions of South and Central America, insular Southeast Asia, Australia, and the western Pacific islands. For much of the 20th century, Citronella was classified under the family Icacinaceae before molecular phylogenetic studies supported its transfer to Cardiopteridaceae.
Members of the genus exhibit a broad geographic disjunction, with species occurring in South America (e.g., Citronella gongonha in Brazil, Paraguay, Uruguay, and Argentina; C. incarum in Peru, Colombia, and Ecuador), the Pacific islands (C. vitiensis in Fiji, C. macrocarpa and C. hirsuta in New Caledonia), and Australia (C. moorei and C. smythii in Queensland and New South Wales). The Chilean species Citronella mucronata is the most cold-hardy member of the genus and the one most frequently encountered in cultivation, having been introduced to Europe as an ornamental. Despite the shared name, Citronella is botanically unrelated to the grass genus Cymbopogon, the commercial source of citronella oil used in insect repellents; the common name derives independently from the French "citronnelle," referencing a lemon-like fragrance associated with some species. Few species have been widely cultivated, and the genus remains relatively obscure in horticulture outside its native range.
Etymology
The genus name "Citronella" is borrowed from the French word "citronnelle", a diminutive form of "citron" (lemon), referring to a lemon-like scent. The name is shared etymologically with the grass genus Cymbopogon — the source of citronella oil — but the two genera are botanically unrelated. The Wikipedia article for the genus explicitly includes a "not to be confused with" notice directing readers to Cymbopogon.
Distribution
Citronella has a broadly disjunct pantropical distribution. Species are native to tropical regions of South and Central America (including Brazil, Chile, Colombia, Peru, Ecuador, Bolivia, Paraguay, Uruguay, Argentina, and Venezuela), insular Southeast Asia and Malesia (Indonesia, New Guinea, Philippines), Australia (Queensland, New South Wales), and islands of the western Pacific (Fiji, New Caledonia, Solomon Islands, Samoa, Tonga). This scattered distribution pattern, with species in both the Neotropics and the Australasian/Pacific region, is a characteristic feature of the genus.
Taxonomy
Citronella was originally described by David Don in 1832. Throughout much of its taxonomic history, the genus was placed in the family Icacinaceae, a now-reorganized assemblage of tropical trees and shrubs. Modern molecular phylogenetic studies have reclassified Citronella into the family Cardiopteridaceae within the order Aquifoliales (APG IV system). Two heterotypic synonyms are recorded: Chariessa (Miquel) and Briquetina (J.F. Macbride). The genus comprises approximately 20 accepted species and is the namesake of its family, though the broader Cardiopteridaceae also includes several other small genera of tropical woody plants.
Cultivation
Few species of Citronella are cultivated. The most noteworthy in horticulture is Citronella mucronata, native to Chile, which is exceptional within the genus for its cold hardiness and has been successfully introduced to European gardens. The remaining species are rarely grown outside their native ranges, and the genus as a whole remains uncommon in cultivation. Citronella gongonha, the type species from South America, produces edible fruits used locally, though it is not widely cultivated for this purpose.
