Baccharis L. is a large genus of flowering shrubs and perennial herbs in the daisy family (Asteraceae), placed in subfamily Asteroideae, tribe Astereae. Named by Linnaeus in 1753, it comprises somewhere between 250 and 400 accepted species — with GBIF recognising 702 total descendant taxa including infraspecific forms — making it one of the largest genera in Asteraceae in the Western Hemisphere.
Plants are almost all dioecious (male and female flowers borne on separate individuals), the rare exception being Baccharis monoica. Leaves are alternate along the stems when present, and the small flower heads bear only disk florets — typically white or pinkish — with no showy ray flowers. Stems are often resinous and can range from 10 cm to 6 m tall depending on species. Many species produce dense, flexible woody stems and small leaves that superficially resemble brooms, though they are unrelated to true brooms.
The genus is distributed throughout the Americas, with its greatest diversity in South America — particularly Brazil, Argentina, Colombia, Chile, and Mexico. B. halimifolia extends the range northward along the Atlantic Coast of North America as far as Nova Scotia, Canada. Habitats span a wide spectrum: many species favour wet sites such as stream banks, washes, ditches, and marshes, while others colonise open, disturbed, or overgrazed land.
Ecologically, Baccharis plays several roles. Numerous species produce abundant nectar and are important honey plants, with B. dracunculifolia being a primary source of Brazilian green propolis. Lepidoptera larvae use various species as host plants. Some species, notably B. conferta, have been used as nurse plants in climate-change-assisted migration experiments for high-altitude Mexican fir forests. At the same time, B. coridifolia is toxic to livestock, causing gastrointestinal necrosis, and several species — most notably B. halimifolia — have become invasive outside the Americas, particularly along Australia's eastern coast and in Spain.
Etymology
The genus name Baccharis was coined by Linnaeus in 1753 and is derived from Bacchus (Dionysus), the Roman god of wine. The connection likely reflects ancient use of the name for aromatic plants in Mediterranean antiquity, which Linnaeus applied to this New World genus.
Distribution
Baccharis is a New World genus with roughly 400 species distributed across tropical and warm-temperate regions of North, Central, and South America. Diversity is greatest in South America, particularly in Brazil, Argentina, Colombia, Chile, and Mexico. In North America, B. halimifolia extends along the Atlantic and Gulf coasts northward to Nova Scotia, Canada.
Within those ranges, species occupy a broad array of habitats — wet ground near stream banks, washes, ditches, and marshes is characteristic for many, while others colonise open, disturbed, or overgrazed land. Altitudinal range is considerable, with montane species present in the Andes.
Ecology
Many Baccharis species inhabit riparian corridors and moist disturbed ground such as ditches and stream margins. Stems are typically resinous and glabrous, and some species produce rhizomes. The genus is generally unpalatable to cattle and can expand aggressively on overgrazed rangelands; B. pteronioides presents livestock hazard concerns in the southwestern United States, and B. pilularis spreads into degraded California and Oregon pastures.
The flowers are rich in nectar; B. dracunculifolia in particular is the main botanical source of Brazilian green propolis and a major resource for Africanised honeybees. Multiple Lepidoptera species use Baccharis as larval host plants. B. conferta has been studied as a nurse-plant species to protect Abies religiosa seedlings during assisted migration experiments under climate change scenarios in Mexico.
B. coridifolia is toxic to several livestock species, causing necrosis of the gastrointestinal tract in cattle, horses, sheep, and rabbits.
Cultivation
Several Baccharis species are cultivated for landscape use, particularly for erosion control, windbreaks, and habitat restoration. The dense, flexible branching of many species makes them effective windbreak plants. B. pilularis (coyote brush) is widely used in California native-plant landscaping and erosion control on slopes.
B. genistelloides (carqueja) is cultivated in subtropical to tropical gardens (USDA zones 9–12) for its medicinal properties and as an evergreen perennial to approximately 2 m in height and spread. It prefers full sun and moist to wet, fertile soil but adapts to various soil types.
Propagation
Baccharis species are propagated primarily from seed. Cuttings are also used in horticultural practice, particularly for clonal propagation of desirable female or male forms (important given the dioecious nature of the genus). For B. genistelloides, seed propagation under warm conditions is documented.
Conservation
Northern Andean Baccharis populations are considered at risk from ongoing habitat destruction. B. halimifolia populations at the northern edge of their range in Nova Scotia, Canada, receive conservation attention as range-limit populations.
Conversely, B. halimifolia and related species have become invasive outside the Americas — notably along Australia's eastern coast, where biological control research has been initiated — and in parts of Spain. B. pilularis also spreads into degraded California and Oregon rangelands, where it can displace native vegetation.
Cultural Uses
Baccharis species have a long history of use in traditional medicine throughout Latin America. B. genistelloides (carqueja) contains high concentrations of flavonoids — up to 20% by weight, including quercetin, luteolin, nepetin, apigenin, and hispidulin — and has been used by indigenous rainforest peoples to treat a wide range of ailments. Documented traditional and ethnobotanical applications include liver and gallbladder disorders, digestive complaints, diabetes management, hypertension, stomach ulcers, malaria, intestinal parasites, kidney disorders, and inflammation. Laboratory studies show antiviral activity against herpes simplex, and 3,5-dicaffeoylquinic acid from the genus has been investigated for potential HIV inhibition.
B. dracunculifolia is the primary botanical source of Brazilian green propolis, a resinous hive product produced by Africanised honeybees with documented antimicrobial and anti-inflammatory properties. Chilean and Argentinean species contain the terpenoid compound viscidone, reflecting the genus's broad secondary chemistry.
Taxonomy Notes
Baccharis was formally described by Linnaeus in his Species Plantarum (1753, p. 860). It belongs to the family Asteraceae, order Asterales, in the subfamily Asteroideae and tribe Astereae. GBIF recognises its taxonomic status as accepted, with 702 descendant taxa (species plus infraspecific taxa). Most authorities accept 250–400 species.
Nearly all species are dioecious — individual plants bear either staminate or pistillate heads, not both — making Baccharis monoica a noted exception. Related genera within Astereae include Archibaccharis and Heterothalamus. Key characters for species delimitation include habit, branching structure, leaf shape and margins, vestiture, head arrangement, and the number of nerves on the cypselae (achenes); collectors are advised to gather both male and female specimens.
