Of course, there are plenty of garden legumes from other parts of the world: chickpeas, lentils, mung beans, rice beans, and the like. I have grown all of them and can speak from experience about one glaring downside: You need to plant a lot of lentils or chickpeas in order to harvest a bushel of seeds. For these crops, you need to think in terms of a small field, which is fine if you are interested in commercial-scale production but impractical in a small backyard garden.
Native Americans grew beans because the input was minimal yet the harvest was plentiful, not to mention that they could grow them among the hills of corn, using the cornstalks as support for the twining vines. Native peoples planted many types of beans to meet various dietary needs, such as grinding for flour or cooking to form pastes incorporated into dumplings. It is helpful to keep these original uses in mind when growing heirloom varieties, because not all heirloom beans cook the same way as modern hybrids that were developed for tender pods.
Common garden beans (Phaseolus vulgaris) are divided into two basic groups: pole beans and bush beans. Among heirloom varieties is a third group called semi-pole, which form low bushes but also send out runners at the top that require some kind of support. The nutritional value of pole beans and bush beans is generally the same, although some pole beans produce larger, meatier beans than the common bush varieties. Bush beans are nothing more than dwarf selections of pole beans, whose long vines are closer in growth habit to their wild ancestors. Bush beans generally ripen earlier than pole beans, so they are ideal for short-season areas. Commercial growers favor them for this reason and because the bush types are more easily machine harvested. For an extended steady harvest, plant successive rows of bush beans at one-week intervals.
Some of the early bean books, such as Georg von Martens’s Gartenbohnen (Garden Beans, 1869) and U. P. Hedrick’s Beans of New York (1931), tried to sort out the bean story and categorize beans by seed shapes, seed colors, pod shapes, pod colors, and a host of other physical characteristics that were artificial, having been induced by humans through breeding rather than through genetic affinities. The result was a veritable Tower of Babel of bean names, especially among the landraces developed by country people, who simply gave them local monikers. In other cases, commercial varieties gained multiple names. For example, ‘Landreth’s Stringless Bush’, a popular variety introduced in 1885 by the Landreth Seed Company, is identical to the ‘Kiva Bush’ grown widely by Indians in the Southwest. The Pueblo peoples still use this bean in religious rituals. In spite of their sometimes-confusing names, I prefer to grow heirloom varieties because I am attracted by their stories (a useful hook in getting kids interested in kitchen gardening). Furthermore, the range of flavors in the old heirlooms simply cannot be beaten.