Phaseolus is a genus of roughly 70 species of herbaceous to woody annual and perennial vines in the legume family Fabaceae (order Fabales). All species are native to the Americas, with the greatest diversity centred in Mesoamerica, making Phaseolus one of the few major crop genera entirely of New World origin.
The genus is among the most economically significant of all legumes. Five species were domesticated by Indigenous peoples of the Americas long before European contact: the tepary bean (P. acutifolius), runner bean (P. coccineus), year bean (P. dumosus), lima bean (P. lunatus), and the common bean (P. vulgaris). Of these, the common bean is today cultivated on every inhabited continent across tropical, subtropical, and temperate regions, forming a dietary staple for hundreds of millions of people worldwide.
Morphologically, Phaseolus plants are climbing or twining vines, though some species are more bushy and erect. Flowers are typically papilionaceous (butterfly-shaped), characteristic of the subfamily Papilionoideae, and produce elongated pods containing two to several seeds.
Taxonomically, the genus was formally described by Carl Linnaeus in 1753 in Species Plantarum. Later revisions reassigned many Old World species formerly placed in Phaseolus to the closely related genus Vigna; the mung bean, for instance, was long known as Phaseolus aureus before being reclassified as Vigna radiata. Modern phylogenetic studies organise the ~70 accepted Phaseolus species into eight clades, confirming the genus as strictly endemic to the New World.
Etymology
The name Phaseolus was coined by Linnaeus in 1753, derived from the Latin phaseolus, itself a diminutive of phasēlus, borrowed from the Greek φάσηλος (phasēlos) — a term applied to certain Old World bean-pod plants of unknown ultimate origin. After the Columbian exchange introduced New World beans to Europe in the 16th century, the name was applied to these newly encountered species, culminating in Phaseolus vulgaris for the common bean.
Distribution
All species of Phaseolus are native to the Americas, with the centre of diversity in Mesoamerica. The genus is entirely absent from the Old World in the wild. The common bean (P. vulgaris) has been widely introduced through cultivation and is now grown in tropical, subtropical, and temperate regions worldwide.
Ecology
Phaseolus species serve as larval food plants for several Lepidoptera, including the common swift, garden dart, ghost moth, Hypercompe albicornis, H. icasia, and the nutmeg moth. As legumes, Phaseolus plants fix atmospheric nitrogen through symbiosis with soil bacteria, enriching the soils in which they grow.
Cultivation
The five domesticated Phaseolus species — common bean (P. vulgaris), lima bean (P. lunatus), runner bean (P. coccineus), tepary bean (P. acutifolius), and year bean (P. dumosus) — are among the world's most widely grown food crops. Common beans are grown as both bush and pole (climbing) varieties and are cultivated across a broad range of climates. Tepary beans are notably drought-tolerant, making them important in arid regions of Mexico and the southwestern United States.
History
Phaseolus beans have been cultivated in the Americas for thousands of years, with archaeological evidence of domestication dating to at least 7,000–8,000 years ago in Mesoamerica and the Andes. They were a core component of the "Three Sisters" polyculture (beans, maize, squash) practised by many Indigenous peoples of North and Central America. Following the Columbian exchange, common beans and lima beans spread rapidly through Europe, Africa, and Asia, transforming cuisines and agricultural systems across the globe.
Taxonomy Notes
Numerous species once placed in Phaseolus have been reclassified into the related genus Vigna. Notable examples include the mung bean (formerly Phaseolus aureus, now Vigna radiata) and the snail bean (Vigna caracalla, moved in 1970). The modern, phylogenetically circumscribed Phaseolus is strictly a New World genus, with approximately 70 species organised into eight clades. The genus was first formally described by Linnaeus in Species Plantarum (1753).
