Apios americana, sometimes called the American groundnut, potato bean, hopniss, Indian potato, hodoimo, America-hodoimo, cinnamon vine, or groundnut (not to be confused with other plants in the subfamily Faboideae sometimes known by that name) is a deciduous or evergreen perennial vine that bears edible beans and large edible tubers.
Description
The vine of American groundnut can grow to long. It has pinnate leaves long with 5–7 leaflets.
The flowers are usually pink, purple, or red-brown, and are produced in dense racemes in length.
Genetics
The species is normally 2n=2x=22, diploid, but both diploid and triploid forms exist. Thus, triploids are entirely dependent on tuber division for propagation whereas diploids can be propagated through both seeds and tubers. A few diploids have been found in the northeastern part of the range, such as along the Black River in Central Ontario.
Ecology
The species is a larval host for the Epargyreus clarus. Leafcutting bees from the family Megachilidae are the only pollinator that has been identified, though it has been speculated that the plant is also pollinated by flies.
Nitrogen fixation
American groundnut fixes its own nitrogen, which could be a great advantage in comparison to other roots crops, such as potatoes, true yams, and sweet potatoes. These do not fix their own nitrogen and require large applications of nitrogen fertilizer or cover cropping with nitrogen fixing plants. American groundnut can be nodulated by bacterial strains that are normally found in symbiosis with soybeans or cowpeas. So, from a permacultural perspective, Native Americans may well have "cultivated" the groundnut. Evidence suggests the Shawnee tribe cultivated it with corn and squash in a method known as three sisters gardening. Apios would provide nitrogen for the heavy-feeding squash.
In 1985, Dr. William J. Blackmon, Dr. Berthal D. Reynolds, and their colleagues at Louisiana State University in Baton Rouge, Louisiana, began a program of deliberate domestication of American groundnut. Their primary goal was to develop an American groundnut that can produce a significant yield in a single season. Of these lines, only 53 genotypes were kept for further analysis. Three different locations and three different growing conditions—field, pots, and grow-bags—were used. There was significant variation found among almost all of the 20 genotypes in the field growing condition. Inter-node length, plant vigor, and stem diameter during plant growth were positively correlated with the plant yield below ground.
Despite these efforts at domestication, the American groundnut remains largely uncultivated and underused in North America and Europe. There seems to be a partial self-incompatibility with Apios breeding and manual pollinations, resulting in rare seed-sets. The crop has small tuber size for most genotypes. American groundnut was introduced, accidentally or deliberately, to Japan during the Meiji era (1868–1912). One theory is that it was accidentally brought to Japan as a stowaway weed among apple seedlings imported from North America. Although American groundnut agriculture is primarily identified with agriculture in the Aomori prefecture, it is grown in the nearby prefectures of Akita and Miyagi as well.
An important part of the spread and popularization of American groundnut consumption in Japan has been the efforts of Dr. Kiyochika Hoshikawa to promote the cultivation of this crop in Japan, and the flurry of scientific articles on the health benefits of eating American groundnut tubers. There are reports of American groundnut cultivation in South Korea as well, where it is grown for its nutritional benefits.
Critical agronomic constraints
Mechanical harvesting represents the primary barrier to commercial viability. Modified potato harvesters damage thin-skinned tubers and miss irregularly positioned ones. Hand-harvest labor requirements (40-80 hours/ha) render large-scale production economically unfavorable.
The perennial establishment period requires 2-3 growing seasons for economically viable yields, delaying return on investment compared to annual crops. Vining growth habit necessitates support structures costing $2,000-5,000/ha, though the species fixes atmospheric nitrogen through rhizobial symbiosis, eliminating nitrogen fertilizer requirements. Nitrogen fixation contributes 50-150 kg N/ha annually to soil fertility.
The species exhibits excellent cold hardiness (USDA zones 3-9) and pest resistance with minimal disease pressure. providing strong nutritional rationale for development despite agronomic challenges.
Louisiana State University Breeding Program
The most comprehensive domestication effort occurred at Louisiana State University from 1985 to 1994 under Dr. William Blackmon and Berthal Reynolds. though commercial tissue culture was never implemented. Genomic characterization identified six genotypic clusters and marker-trait associations for tuber size, architecture, and maturity. For example, in Europe, where the crop is still relatively unknown, its nutritional profile could make it valuable for both human nutrition and livestock feed.
The groundnut is notable for its nutritional value, multiple edible plant parts like tubers and seeds, its ability to fix nitrogen, perennial growth habit, tolerance of wet soils, and adaptability across eastern North America.
Farming and cropping systems
The groundnut may be particularly interesting for subsistence smallholder farmers due to its climbing growth (limited space for food cultivation) and ability to fix nitrogen (limited input cultivation).
Ethical and societal considerations
From an agroecological and historical perspective, traditional knowledge associated with groundnut cultivation by Indigenous Americans should be acknowledged according to the FAO (2010). Historical records indicate that after European colonization, local regulations restricted Native Americans from harvesting groundnuts on lands claimed by colonists. Recognizing this historical context is important, along with ethical considerations such as the protection of Indigenous rights, prevention of biopiracy, and compliance with international agreements such as the Nagoya Protocol, which governs access to genetic resources and the fair and equitable sharing of benefits arising from their utilization. Its use for human consumption versus livestock feed should also be debated.
Toxicity
Studies in rats suggest that raw tubers should not be consumed. They contain harmful protease inhibitors that are denatured by cooking.
Uses
The tubers and seeds can both be cooked and eaten, the former in the manner of potatoes and the latter like peas.
Indigenous peoples of the Americas
The tubers have traditionally been a staple food among most Indigenous peoples of the Americas within the natural range of the plant. In 1749, the travelling Swedish botanist Peter Kalm wrote, "Hopniss or Hapniss was the Indian name of a wild plant, which they ate at that time... The roots resemble potatoes, and were boiled by the Indians who ate them instead of bread." Many tribes peel them and dry them in the sun, such as the Menomini who have traditionally built scaffolds of cedar bark covered with mats to dry their tubers for winter use. In 1623, the Pilgrims, "having but a small quantity of corn left," were "enforced to live on groundnuts... and such other things that the country afforded... and were easily gotten..." The groundnut was likely eaten at the harvest festival of November 1621 that is regarded as the first Thanksgiving, although only venison was specifically named as a food item at this meal by a Pilgrim eyewitness account.
Philosopher Henry David Thoreau commented on the nutty flavor and dry texture in October 1852. A. americana tubers were found to have a protein concentration of , similar to that of other species in the genus, A. carnea and A. fortunei. The fresh weight of a tuber is 36% of carbohydrate (primarily starch). The tuber has more of these types of carbohydrates than the soybean, potato, and sweet potato. Extract from the American groundnut was shown to drive the anti-oxidative pathway in cells although it did not have anti-oxidative activity itself. Consumption of the flower was shown to lower plasma glucose levels in diabetic mice.