Phaseolus coccineus, known as runner bean, scarlet runner bean, or multiflora bean, is a plant in the legume family, Fabaceae. Another common name is butter bean, which, however, can also refer to the lima bean, a different species.
This species originated from the mountains of Central America. Most varieties have red flowers and multicolored seeds (though some have white flowers and white seeds), and they are often grown as ornamental plants. The vine can grow to 3 m (9 ft) or more in length. It differs from the common bean (P. vulgaris) in several respects: the cotyledons stay in the ground during germination, and the plant is a perennial vine with tuberous roots (though it is usually treated as an annual). The knife-shaped pods are normally green; however, there are very rare varieties bred by amateurs that have very unusual purple pods. An example of such a purple-podded runner bean is 'Aeron Purple Star'. Runner beans have also been called "Oregon lima bean", and in Nahuatl ayocotl or in Spanish ayocote. Runner beans, like all beans, contain the toxic protein phytohaemagglutinin and thus should be cooked well before eating.