Groundnuts
The groundnut is known by many names; the earthnut, tekeneipen, Indian potato, potato bean, hopniss, or by many aficionados, simply Apios. A nitrogen-fixing root crop, it has captured the attention of humans for thousands of years. It was one of the earliest native crops to find its way to Europe, documented as early as 1585.1 Part of Fabaceae, it is included in the pea family, and while the beans themselves are not seen as a primary crop, it is a reminder of the historical ecological role they play in the ecosystem.
Now, unlike many of the species we have covered to date, apios doesn’t appear to have any unique specialist relationships with pollinators; leaf cutter bees and honeybees have been documented extensively on the flowers, and those still seem to have poor reproductive success, suggesting that if they had co-evolved with any specialist pollinator, it no longer exists.2
The genus Apios comprises three species native to Asia and two species found in North America. Apios americana is native to Eastern North America from New Brunswick, Canada to Florida and as far west as Texas, thriving in waterlogged soils. Thomas Harriot, who accompanied Sir Walter Raleigh on his expedition in 1584, describes “Openauk”, which are a root “of the bigness of walnuts” that are “fastened with a string” that were boiled for consumption.3 Over a thousand miles north, in New England, John Brereton describes the same, stating that “in every Island, and almost in every part of every Island, are great store of Groundnuts, fortie together on a string, some of them as bigger as hennes eggs.”
Colonel James Smith, under captivity by the Delawares, describes eating the potatoes boiled and dipped in raccoon fat. They were boiled alone, cooked with meat or corn, or roasted directly in hot ashes. The Menominee made preserves by boiling the tubers in maple syrup. The groundnut was primarily a food for the summer, according to early reports, they were often eaten in June, July, and August, alongside berries and fish. However, there are reports of tubers peeled and dried for winter storage— sometimes in maple syrup, and even more described as a winter food in places like modern Virginia. This speaks to the capacity of the groundnut to fill a variety of niches within a community’s diet based on the local ecological conditions, and why the plant was so valued by Indigenous communities.
The plants themselves danced between crop and wild-harvested food. According to William Cronon, groundnuts were harvested wild but also planted along hunting trails and clearings in the forest, providing accessible food regardless of the hunt’s success.4 They were considered not a domesticated crop but not quite wild, either. Given their prominence in the diets of so many Indigenous communities, tubers have been dug up on several sites, from Red Cloud Nebraska, near a historical Pawnee village, and from four Ozark sites. On one particular site in Mississippi, groundnuts were found alongside corn, suggesting that the food was still significant even after corn had arrived, which had fundamentally altered the food production of indigenous people across the East Coast.5
The landscapes around Indigenous settlements were often managed to support food-producing plants; we’ve covered the extensive selection for hickories, oaks, chinquapins, black walnuts, and butternut, but underneath the canopy in wet regions where the black walnuts called home were pawpaws, groundnuts, spicebush, and more. Colonists described arriving at hunting campsites where Indigenous hunters had dug up massive stretches of groundnuts, a reminder that hunting paths were filled with edible plants similar to the areas around their settlements.
A common trend that we have seen discussing native crops is that apios shows two primary ‘lines’ of genetics; a triploid form that predominated the northern range of the species and a diploid form for much of the south. It is suggested that a combination of the triploid and self-incompatibility is the cause of the sterility of the species over much of the range.6 Historically, it was assumed that the driver for the infertile nature of northern species was the season length— however that doesn’t seem to be the case, and it is instead driven by its ploidy status.
As shown in the graph above, Apios in the United States are split into two species; “Medikus” and “Robinson”. Medikus is the groundnut most folks reading this are familiar with, while Robinson is, today, an extremely rare species that offers much less in terms of human consumption.7 A. priceana primarily grows in rocky open woodlands, while A. americana thrives in forests, thickets, prairies, riverbanks, and wetlands.
While the groundnut fed the starving pilgrims during their first winter, it has never captured much of the attention of the nation, despite the later successes of blueberries, pecans, and strawberries. However, in 1985, serious research into the viability of Apios as a crop was led by Bill Blackmon & Berthol Reynolds at the Louisiana State University Agricultural Experiment Station in Baton Rouge, Louisiana. The program was short-lived— it continued for 9 years until 1994— despite its successes. Blackmon moved away for personal reasons and later commented that he would not have left if he knew the program wouldn’t continue without him— in his words, “I left LSU. I thought they were going to let Bert continue. Bert, because of his name, continued to work with this plant but they kind of moved him to doing something else else”.8 Without their leadership, the LSU project was considered dead.
The germplasm for this project was collected as seed from primarily the lower Mississippi Valley. Of the 20,000 plants propagated, only a handful were selected for potentially useful breeding material, including LA85-034.9 The program expanded and eventually had germplasm from 19 states. Today, the byproduct of this research can be found in the “LSU” (LA85-034) groundnut selection, widely available online.
Work is still being done to breed improved varieties, and a collection of at least 53 accessions remains from the Blackmon-Reynolds breeding work at the United States Department of Agriculture in Ames, Iowa. In 2010, the breeding work continued, and in 2013 a subset of the collection was evaluated in Virginia & Pennsylvania to assess the effect of environmental variation on genotype performance. Genotype 1972 was the highest yielding of all genotypes, producing yields similar to sweet potato and yam, producing 3.34 pounds on one plant, largely because it produced the largest ‘child tuber weight’ (the secondary, smaller tubers on the string).10
Part of the improvement of apios as a potential crop isn’t just focused on root size, but reduced vining, reduced stolon length (the “string”), and fewer, larger tubers. With this in mind, nine genotypes have been identified from this project and will be bred for future improvements, including 1972, 2191, 898, 2127, 1849, 2155, 2201, 1970, and 2065. The hopes are that the size of 1972 can be paired with the other amenable traits of the other selections, creating an easier-to-harvest, perennial tuber that fixates nitrogen into the soil.
Part of the challenges of propagating improved selections quickly stems from the ability to rapidly scale the highest-yielding varieties. Today, the easiest way to rapidly propagate improved selections is through the utilization of cuttings with multiple nodules, rooted in water.11 This offers Apios another unique tool in that while the tubers may take two years to produce, propagation is significantly easier than many root crops.
Apios is special because it doesn’t require many fertilizers; the challenge is that the crop requires two years to grow to full size. While it can be difficult to produce significant viable seeds, the genetics are extremely diverse, which has helped accelerate the breeding work to find improved varieties. This also offers unique breeding opportunities, as evidenced by Ken Asmus’s breeding work at Oikos Tree Crops.
Of note from Ken is their capacity to grow very close to the surface, allowing for deeper root crops to layer with them, such as sunchokes. Their vines, which die off quickly from a light frost, are light and don’t put heavy weight on what they climb, offering a myriad of potential polycrop design choices, although they can grow extensive vines, reportedly up to fifty feet long (although I’ve never personally seen any nearly close to this). I have had success growing these alongside sunflowers, which offer strong trunks to carry the vines, and with their extreme heights, don’t necessarily demand significant management.
Ken isn’t the only breeder working to improve the groundnut; researchers in South Korea identified the ‘Jeju’ groundnut, based on an improved variety discovered during research, named after the island where the research was conducted.12 The Experimental Farm Network also offers other improved varieties, including ‘Billington’, a hardy variety from Montana.
You’ll often see, if you’re looking to buy plants online, that many folks advertise selling plants from New Jersey— this isn’t a coincidence, but a reminder of the split between the diploid and triploid genetics. While the triploid are sterile, and the diploid are significantly less common further north, I have personally grown seeds from groundnuts collected here in Massachusetts.
If you’re looking to harvest and propagate your own selections, you’ll be most likely to find them near small ponds or rivers. Typically, they like sandier soil, and their vines are often nestled around small bushes, and unfortunately often around poison ivy. Their vines dry by the mid-fall, and are brittle to the touch. Their leaves are a giveaway, and often if you can get your finger into the soil an inch or so, you’ll find the first tuber to dig up. The seeds require that you wait until the pods are browned to harvest, or they won’t germinate.
On Health
What makes apios so significant from a health perspective? The tubers contain three times the crude protein content of a potato, making up over 16% of its dry weight.13 For this reason, it has been grown as a crop in places like Japan, despite the fact it is not consumed readily in its native country. It’s often ground into flour and mixed into baked goods for improved nutritional profiles. As noted above, it’s also popular in South Korea, and extensive research into its health benefits are being done by Chinese scientists.
It’s no surprise; even without its high protein content, apios also offers a number of health benefits; it has been documented to have anti-inflammatory effects to reduce oxidative damage as well as anti-diabetic effects from the lipinalbin A compound.14 It’s been documented to reduce blood pressure and even alleviate lung inflammation from the influenza virus H1N1.15 The preliminary data goes on and on, and as more research is done, we will have a better idea of its potential to improve the general health of society, should it have the opportunity to find its way into our diets.
If you’ve enjoyed this piece, which is equal to a 9-page chapter, of (so far) a 1290-page book with 957 sources, you can support our work in several ways. The first is by sharing this article with folks you think would find it interesting. Second, you can listen to the audio version of this article in episode #252 of the Poor Proles Almanac wherever you get your podcasts. If you’d like to financially support the project, and get exclusive access to our limited paywalled content, you can become a paid subscriber on Substack or Patreon, which will both give you access to the paywalled content and in the case of Patreon, early access to the audio episodes as well.
Seabrook J A. A biosystematic study of the genus Apios fabricius (Leguminosae) with special reference to Apios americana Medikus. MS Thesis; University of New Brunswick. Fredericton, NB, Canada, 1973.
Westerkamp, C. & Paul, H. Apios americana, a fly-pollinated papilionaceous flower? Pl Syst Evol 187, 135–144 (1993).
Beardsley G (1939) The Groundnut as used by the Indians of eastern North America. Papers of the Michigan Academy of Sciences, Arts and Letters 25:507-525.
Cronon, William. Changes in the Land : Indians, Colonists, and the Ecology of New England. New York :Hill and Wang, 1983.
Caddell, Gloria May, 1981, Plant Resources, Archaeological Plant Remains, and Prehistoric. Plant-Use Patterns in the Central Tombigbee River Valley
Seabrook, J. A. E., & Dionne, L. A. (1976). Studies on the genus Apios. I. Chromosome number and distribution of Apios americana and A. priceana. Canadian Journal of Botany, 54(22), 2567–2572. doi:10.1139/b76-276
Woods, M. (2005). A Revision of the North American Species of Apios (Fabaceae). Castanea, 70(2), 85–100. doi:10.2179/0008-7475(2005)070[0085:arotna]2.
See our interview with Bill Blackmon.
Belamkar V, Wenger A, Kalberer SR et al. (2015) Evaluation of phenotypic variation in a collection of Apios americana: An edible tuberous legume. Crop Sci 55:712-726.
Wickremesinhe, E. R. M., W. J. Blackmon, and B. D. Reynolds. "In vitro propagation of Apios americana." HortScience 25.11 (1990): 1439-1440.
Zung, Riu Key, et al. "Preliminary culture evaluation of newly introduced apios (Apios americana M.)." Korean Journal of Plant Resources 18.3 (2005): 424-432.
Cornelio FJP. Protein quality of Apios americana in tubers and seeds. MS Thesis. Louisiana State University, Baton Rouge, LA, 1987.
Qiang Chu, Shuang Zhang, Lushuang Yu, Yonglu Li, Yangyang Liu, Xiang Ye, Xiaodong Zheng, Apios americana Medikus tuber polysaccharide exerts anti-inflammatory effects by activating autophagy, International Journal of Biological Macromolecules, Volume 130, 2019, Pages 892-902,
Sohn, Sung-Hwa, et al. "Apios americana Medik extract alleviates lung inflammation in influenza virus H1N1-and endotoxin-induced acute lung injury." Journal of microbiology and biotechnology 25.12 (2015): 2146-2152.