Campuloclinium is a genus of flowering plants in the daisy family Asteraceae, placed in the order Asterales. The genus was described by Augustin Pyramus de Candolle in 1836 (Prodromus 5: 136) and, per GBIF's taxonomic backbone, comprises around 20 accepted species and infraspecific taxa, native to Mesoamerica and South America.
The only species with a Ploi record, Campuloclinium macrocephalum, is by far the genus's best-documented member and is widely known by its common name, pompom weed. It was originally described as Eupatorium macrocephalum by Christian Friedrich Lessing in 1830 before later being placed in Campuloclinium; the epithet macrocephalum means "large-headed," referring to its showy inflorescence. The species is native to the southern United States, Central America, and South America, but has become notorious as an introduced, invasive weed elsewhere — it is classed as a principal weed in Brazil and, in South Africa, has spread from cultivation as an ornamental and along roadsides into undisturbed climax grassland and wetlands since the 1960s.
Morphologically, Campuloclinium macrocephalum is a rhizomatous perennial with erect, bristly-haired stems to about 1.3 m tall and lanceolate-elliptic, serrate leaves roughly 8 cm by 2 cm. It forms dense basal leaf rosettes that suppress the germination and growth of neighbouring plants, reinforced by allelopathic chemicals it releases into the soil. The plant dies back to its root crown each year and survives winter veld fires, contributing to its persistence as a rangeland invader. Flower heads carry purplish bracts around large, showy pink flowers, followed by black, bristle-tipped achenes.
Because of its invasiveness, the species has been the subject of biological control research, including investigation of moths (Adaina microdactyla, Cochylis campuloclinium), a stem-galling thrips (Liothrips sp.), and a rust fungus (Puccinia eupatorii) that is specific to the species and can kill the whole plant, roots included.
Etymology
The species epithet of the genus's sole catalogued member, macrocephalum, means "large-headed," referring to its showy inflorescence; the plant was originally described under the older name Eupatorium macrocephalum, with "Eupatorium" honouring the ancient Anatolian ruler Eupator Dionysius (Mithridates).
Distribution
Campuloclinium is native to Mesoamerica and South America. Its sole documented species, C. macrocephalum, is native to the southern United States, Central America and South America, and has been introduced to South Africa, where it has become invasive; it is also classed as a principal weed in Brazil.
Ecology
Campuloclinium macrocephalum forms dense basal leaf rosettes and produces allelochemicals that suppress germination and growth of neighbouring plants. It dies back annually to a persistent rhizomatous root crown and survives winter veld fires, allowing it to invade undisturbed climax grassland and wetlands (notably in South Africa since the 1960s). Biological control agents under investigation include Adaina moths, a stem-galling thrips, and the rust fungus Puccinia eupatorii, which is specific to the species and can kill the whole plant.
History
The species now placed in Campuloclinium was first described as Eupatorium macrocephalum by Christian Friedrich Lessing in Linnaea 5(1): 136–137 in January 1830, before later reclassification into the genus Campuloclinium, which itself was described by Augustin Pyramus de Candolle in 1836.
Cultural Uses
Campuloclinium macrocephalum has been cultivated as an ornamental in South Africa, from where it spread to roadsides and, eventually, natural grassland and wetland habitats.
Taxonomy Notes
Campuloclinium DC. belongs to family Asteraceae, order Asterales; it was published by de Candolle in Prodromus 5: 136 (1836). GBIF's backbone lists about 20 accepted species/infraspecific taxa in the genus. Campuloclinium macrocephalum carries numerous synonyms reflecting a complicated taxonomic history, including Chromolaena pratensis, Eupatorium donianum, and several Eupatorium macrocephalum varieties.
