Subterranean Treasures: the Beneficial Roots of Native Vines

By Angela Magnan

As I pulled into the parking lot next to the native plant collection at work one day, I noticed our intern up in a tree cutting down a native honeysuckle vine. Uh-oh, I thought. Not again! Working at a public garden, our attempts to grow vines can often be frustrated by well-meaning visitors and volunteers, and yes, overly enthusiastic interns, who automatically think that all vines are weeds and cut or pull out the vines we have planted there. 

Apios in August by Angela MagnanOne strategy to avoid such tragedies is to plant vines that are less obtrusive and that produce underground structures from which they will resprout. One such vine is Apios americana, or groundnut. This leguminous, sprawling perennial vine grows up to 10 feet long and produces clusters of maroon pea-type flowers. Used by native peoples east of the Mississippi as a food source, it has both edible seeds and edible tubers.  The seeds are in long pods that can be harvested in the fall when dry and contain as much protein and fiber as pinto beans. Although not commonly grown in the US, it has been commercially farmed in Japan for more than a hundred years. 

The tubers, which grow every 10-12 inches along the rhizomes, need to be cooked and can be eaten in similar ways to potatoes. Research has also shown that dried and powdered tubers have some promise as an additive to gluten free bread products, increasing the protein content and improving the texture. If you harvest the tubers, the plant won’t come back, but it does seed around; you can maintain its presence in your garden by harvesting sparingly. The tubers are a good source of proline, an amino acid that helps build collagen. Groundnuts have been made into a poultice and used by New England tribes to treat proud flesh, a skin condition caused by inadequate healing of wounds that is particularly common in horses. 

Another native vine with a subterranean edible is hog peanut or ground bean. Also a legume, this is a great plant for botany geeks. Its scientific name, Amphicarpaea bracteata, refers to its production of more than one type of flower, a characteristic known as amphicarpy. It has two types of aboveground flowers and a third type underground. One of the aboveground flowers and the underground flower are cleistogamous, meaning they are permanently closed and self-fertile. The second aboveground flower is a delicate white or light purple pea-like flower that is pollinated by bumblebees. This annual or short-lived perennial produces edible underground seeds, but the aboveground seeds are not edible.

In the wild, this plant typically grows along streams and given enough moisture in the garden, it can run rampant and smother nearby plants. If grown strictly for ornamental purposes, this could be undesirable, but if you want to eat the seeds, you can harvest it aggressively and it will still come back. Because it gets a late start during the growing season, it is a great companion for early spring plants that go dormant by mid-summer. If it has something to twine around, it will, but it will also sprawl along the ground as a groundcover. 

In the US, Cherokee and Iroquois people used the plant for intestinal distress. The Cherokee also used it as a snake bite remedy and the Iroquois used it to treat tuberculosis. In Mexico, indigenous peoples grow it amidst maize and beans, allowing it to twine up the maize stems and intermingle with the climbing beans. Referred to as talet beans, they harvest the underground seeds in early spring before planting that year’s maize crop and then roast the beans as a snack. The aboveground seeds are plowed into the soil for next year’s crop. 

Yet another native vine with useful underground structures is Dioscorea villosa, a wild yam whose tubers contain diosgenin. In the 1940’s, scientists figured out how to synthesize human steroid compounds from diosgenin, a process that was then used to manufacture oral contraceptives and cortisone. Today scientists can synthesize diosgenin in the laboratory, but prior to 1970, wild yam was the sole source of diosgenin and most steroid hormones used in modern medicine were developed from this plant. Although diosgenin can be converted into such steroids in a lab, this process does not occur naturally and consuming wild yam would not have the same effect. 

The flowers of Dioscorea villosa are inconspicuous, but it has attractive heart shaped leaves. Even though its long runners can lead it to pop up in unexpected places, it is not aggressive like some of its non-native relatives. The tubers have an unpleasant, bitter taste, and you wouldn’t want to eat them, but they have been used medicinally for various ailments. Native Americans used a root-based tea to treat menstrual cramps, labor pains, inflammation, asthma, and rheumatism. European settlers used it to treat colic, which led to one of its other common names of colic root. It continues to be used in modern herbal medicine as an anti-inflammatory, either dried in capsule form or as a liquid extract to be made into an herbal tea.

The best thing about all three of these vines is that if a well-meaning individual cuts one down, you might still be able to use the underground treasures or leave them be and let the vine grow back. And what about the native honeysuckle cut down by our intern? It was not so lucky; it never came back. 

Photo credits: 1) Apios americana in August (courtesy of author); 2) Amphicarpaea bracteata flowers (Fritzflohrreynolds via Wikimedia Commons); 3) Amphicarpaea bracteata foliage (R. A. Nonenmacher via Wikimedia Commons); 4) Dioscorea villosa twining up hemlock (courtesy of author)

References:

Foster, S. & Johnson, R. (2006). Desk reference to nature’s medicine. National Geographic.

Frey, D. & Czolba, M. (2017). The food forest handbook. New Society Publishers.

Ichige, M., Fukuda, E., Miida, S., Hattan, J., Misawa, N., Saito, S., Fujimaki, T., Imoto, M., & Shindo, K. (2013). Novel isoflavone glucosides in groundnut (Apios americana Medik) and their antiandrogenic activities. Journal of Agricultural and Food Chemistry, 61 (9), 2183-2187. https://pubs.acs.org/doi/10.1021/jf305233t

Ito, S. & Arai, E. (2021). Improvement of gluten-free steamed bread quality by partial substitution of rice flour with powder of Apios americana tuber. Food Chemistry, 337, 127977. https://doi.org/10.1016/j.foodchem.2020.127977

Pena, F.B., Villalobos, G. Martinez, M.A., Sotelo, A., Gil, L., & Delgado-Salinas, A. (1999). Use and nutritive value of talet beans, Amphicarpaea bracteata (Fabaceae: Phaseoleae) as human food in Puebla, Mexico. Economic Botany, 53 (4), 427-434. https://www.jstor.org/stable/4256226

Salmon, E. (2020). Iwigara: The kinship of plants and people. Timber Press.

Schnee, B.K. & Waller, D. M. (1986). Reproductive behavior of Amphicarpaea bracteata (Leguminosae), an amphicarpic annual. American Journal of Botany, 73 (3), 376-386. https://bsapubs.onlinelibrary.wiley.com/doi/abs/10.1002/j.1537-2197.1986.tb12051.x

Medicinal Disclaimer: It is the policy of The Herb Society of America, Inc. not to advise or recommend herbs for medicinal or health use. This information is intended for educational purposes only and should not be considered as a recommendation or an endorsement of any particular medical or health treatment. Please consult a health care provider before pursuing any herbal treatments.


Angela grew up on a dairy farm in Vermont and has degrees in biochemistry, horticulture, and science writing. She now lives in Maryland and has worked in the Gardens Unit at the US National Arboretum since 2012.