Europe had beans long before the common bean arrived from the Americas
The beans ancient Greeks and Romans ate were Asian species, unrelated to the common bean whose seeds and green pods fill markets today. When Phaseolus vulgaris crossed the Atlantic in the 16th century, Europeans simply filed it under existing words for seeds in a pod. Botanists later moved the Old World species out, leaving Phaseolus a wholly American genus.
The common bean is now the most eaten bean species on Earth. Wild plants are native to the Americas, and people domesticated them twice, around 8,000 years ago, in Mesoamerica and in the southern Andes, which left the crop with two distinct gene pools. Together with squash and maize it forms the Three Sisters, the trio at the heart of indigenous American farming. Local names still echo that history: ayacotl in Nahuatl, búul in Mayan and purutu in Quechua, which became poroto in the Spanish of several South American countries.
Language in Europe has its own layers. The Greek phaselos named Asian beans, and the Romans used phaseolus for small seeds and faba for large ones such as fava beans. Faba is related to a Proto-Germanic word that gave Old English its word bean. Linnaeus, sorting beans in 1753, recognised 11 Phaseolus species.
Every wild common bean climbs, but farmers have bred compact bush beans 20 to 60 centimetres tall as well as pole beans that run 2 to 3 metres. Leaves split into three oval leaflets. Small white, pink or purple flowers pollinate themselves, which helps breeders keep cultivars stable, and pods up to 20 centimetres long hold four to eight kidney-shaped seeds, often mottled in several colours. Stringy-podded varieties are usually grown for dry beans, since stringy green pods do not sell. Seeds stay viable for up to five years.
The plant draws its nitrogen from rhizobia, bacteria living in partnership with its roots. Its genome, spread over 11 chromosome pairs, is among the smallest in the legume family. World output reached 28 million tonnes of dry beans in 2022, India leading with 23 percent, and the crop is grown on every continent except Antarctica.
Source: Phaseolus vulgaris
