Phaseolus polystachios is a member of the Fabaceae (pea family) and is the only wild representative of the Phaseolus genus in temperate North America. Phaseolus is a fairly large genus with many wild species native to Meso-America and South America and include common beans, lima beans and a few other domesticated types. Our Wild Kidney Bean is most closely related to Phaseolus lunatus (Lima beans), and grows as a perennial vine that dies back over the winter.¹ During the summer, it produces long racemes of pinkish to purplish flowers that form small bean pods. These bean pods mature and produce several lentil sized beans in each pod. Pods will shatter (spontaneously split and twist open) in the fall and send beans flying many feet away from the parent plant.
It’s preferred habitat is thickets and openings in dry woodlands where it can climb, reaching for the sun. Historically, it’s range seems to have started in southern New England west to Illinois and south to the Gulf. Unfortunately, this plant seems to be losing ground within it’s native range. I personally have not come across it in the wild, nor have very many people that I know even heard of this little plant. Suggestions as to it’s demise include both habitat loss and bean weevil damage.²
The beans of this plant are edible and have a history of use among Native Americans. Remains of P. polystachios beans have been found in several archaeological sites in Oklahoma and Arkansas. There are even some suggestions that Native Americans may have been selecting seeds that did not shatter open, although this seems to be merely speculation at this point.³
Considering the fragile status of the Wild Kidney Bean, this is not a wild plant to be collected for food, but rather a plant to conserve, tend and protect. Plant breeders look to plants like this as genetic reservoirs, plants that can be used for future breeding projects to keep our gardens and fields producing. The ideal place to conserve a plant like this is in situ, or in it’s original place, but since it’s natural habitat has become increasingly rare we have to find a place for it outside of it’s original home. This is ex situ conservation, or “off site conservation”. Seed banks serve this purpose, as do our personal gardens.
I have found that this plant takes readily to the garden in Pennsylvania, with seeds germinating easily and the plants growing and reproducing without any trouble. Indeed, the shattering pods send seeds into my neighbors yard each fall and I see seedlings sprouting in his lawn each spring. Fortunately for me, he is rather laid back and just mows them down with his grass. Aphids and their tending ants seem to be attracted to the plants, but the plants tolerate them. Pollinators love them and the plants buzz with activity through the second half of summer.
A bonus for keeping these plants alive and well in my garden are the edible seeds, a food that I would not have access to unless I was was tending this plant. The dried beans are collected out of the garden before the pods shatter and are prepared in much the same way we prepare any other dry bean, by soaking and boiling. Changing the cooking liquid half way through cooking eliminate the bitterness that I find with this bean. Immature pods are too fibrous to be eaten as a green bean, and the tiny flowers, while beautiful, are slightly bitter. I like to spike venison chili with cooked P. polystachios beans as I imagine deer browsing the North American woodland thickets, munching on these plants (they certainly love other types of beans in my garden).
The Wild Kidney Bean is a good example of a way to diversify our gardens while helping conserve a wild plant that once seemed to be populous but now struggles in our changing landscape. As gardeners, there are a lot of benefits in making room for plants that have a rightful place in our North American habitat. These native plants often require little care as they are right at home in our environment. They provide pollinator food, variety in our diet, beauty. They co-exist peacefully with my cultivated beans and may even provide future plant breeders and conservationist with materials that can be hard to find in the wild landscape.
If you are interested in trying to grow Wild Kidney Beans in your garden, I offer the seeds on a limited basis through Seeds Savers Exchange.
1: Sarah Dohle, Jorge Carlos Berny Mier y Teran, Ashley Egan, Theodore Kisha, and Colin K. Khoury (2017) Wild beans (Phaseolus L.) of North America. To be published.
2: Ashley N. Egan, The Plant Press, Vol 19-No. 1, Jan-Mar 16
4: Roger Tory Peterson, Margaret KcKenny (1968) Wildflowers Northeastern/Northcentral North America. Boston, MA: Mifflin
5: Lawrence Newcomb (1977) Newcomb’s Wildflower Guide. Little, Brown & Company