Illustration of cornstalk on which bean plants are climbing, surrounded at the base with leaves and fruit of a pumpkin vine
Maize, climbing beans, and winter squash planted together

The Three Sisters (Spanish: tres hermanas) are the three main agricultural crops of various indigenous peoples of Central and North America: squash, maize ("corn"), and climbing beans (typically tepary beans or common beans). In a technique known as companion planting, the maize and beans are often planted together in mounds formed by hilling soil around the base of the plants each year; squash is typically planted between the mounds. The cornstalk serves as a trellis for climbing beans, the beans fix nitrogen in their root nodules and stabilize the maize in high winds, and the wide leaves of the squash plant shade the ground, keeping the soil moist and helping prevent the establishment of weeds.

Indigenous peoples throughout North America cultivated different varieties of the Three Sisters, adapted to varying local environments. The individual crops and their use in polyculture originated in Mesoamerica, where squash was domesticated first, followed by maize and then beans, over a period of 5,000–6,500 years. European records from the sixteenth century describe highly productive Indigenous agriculture based on cultivation of the Three Sisters throughout what are now the Eastern United States and Canada, where the crops were used for both food and trade. Geographer Carl O. Sauer described the Three Sisters as "a symbiotic plant complex of North and Central America without an equal elsewhere".

Cultivation methods

2009 US Sacagawea dollar coin depicting a woman in a buckskin tunic planting seeds among cornstalks and squash plants
The Three Sisters planting method is featured on the reverse of the 2009 US Sacagawea dollar.[1]

Agricultural history in the Americas differed from the Old World in that the Americas lacked large-seeded, easily domesticated grains (such as wheat and barley) and large domesticated animals that could be used for agricultural labor. At the time of first contact between the Europeans and the Americans, Carlos Sempat Assadourian writes that Europeans practiced "extensive agriculture, based on the plough and draught animals" while the Indigenous peoples of the Americas practiced "intensive agriculture, based on human labour".[2]

In Indigenous American companion planting, maize (Zea mays), beans (Phaseolus and Vicia[3] spp.), and squash (Cucurbita pepo) are planted close together. The maize and beans are often planted together in mounds formed by hilling soil around the base of the plants each year; squash is typically planted between the mounds.[4] In the northeastern U.S., this practice increases soil temperature in the mound and improves drainage, both of which benefit maize planted in spring.[4] In Haudenosaunee (Iroquois) farming, the fields were not tilled, enhancing soil fertility and the sustainability of the cropping system by limiting soil erosion and oxidation of soil organic matter.[5] A modern experiment found that the Haudenosaunee Three Sisters polyculture provided both more energy and more protein than any local monoculture.[5]

The three crops benefit by being grown together.[4][3] The cornstalk serves as a trellis for the beans to climb, the beans fix nitrogen in the soil, and their twining vines stabilize the maize in high winds, and the wide leaves of the squash plant shade the ground, keeping the soil moist and helping prevent the establishment of weeds.[6][7] The prickly hairs of some squash varieties deter pests, such as deer and raccoons.[7]

Although this synergy had been traditionally reputed among American cultures, scientific confirmation has arrived only much more recently.[3] Much of this research was performed in the Soviet Union in the early 1970s and published in several volumes of Biochemical and Physiological Bases for Plant Interactions in Phytocenosis edited by Andrey Mikhailovich Grodzinsky [uk; ru].[3] Dzubenko & Petrenko 1971, Lykhvar & Nazarova 1970 and Pronin et al. 1970 find a wide number of leguminous crops increase the growth and yield of maize, while Gulyaev et al. 1970 select later maturing lines of beans to produce the converse effect, increasing even further the yield gain of beans when planted with maize.[3] Pronin et al. 1972 find increased productivity and root exudate in both crops when combining Vicia faba with maize, and even more so in soils with preexisting high nitrogen fixing microorganism activity.[3]

Hopi Blue Corn, Pole Beans, and Sugar Pumpkins at 6000'
Three Sisters mound planting in Arizona, 2022

Indigenous peoples throughout North America cultivated different varieties of the Three Sisters, adapted to varying local environments.[8] The milpas of Mesoamerica are farms or gardens that employ companion planting on a larger scale.[9] The Ancestral Puebloans adopted this garden design in the drier deserts and xeric shrublands environment. The Tewa and other peoples of the North American Southwest often included a "fourth Sister", Rocky Mountain bee plant (Cleome serrulata), which attracts bees to help pollinate the beans and squash.[10] The Three Sisters crop model was widely used by a number of First Nations in the Great Lakes–St. Lawrence Lowlands region.[11]


European records from the sixteenth century describe highly productive Indigenous agriculture based on cultivation of the Three Sisters throughout what are now the Eastern United States and Canada, from Florida to Ontario.[5] The geographer Carl O. Sauer described the Three Sisters as "a symbiotic plant complex of North and Central America without an equal elsewhere".[12] The agronomist Jane Mt. Pleasant writes that the Three Sisters mound system "enhances the soil physical and biochemical environment, minimizes soil erosion, improves soil tilth, manages plant population and spacing, provides for plant nutrients in appropriate quantities, and at the time needed, and controls weeds".[4] After several thousand years of selective breeding, the hemisphere's most important crop, maize, was more productive than Old World grain crops. Maize produced two and one-half times more calories per given land area than wheat and barley.[13]

Nutritionally, maize, beans, and squash contain all nine essential amino acids.[5] The protein from maize is further enhanced by protein contributions from beans and pumpkin seeds, while pumpkin flesh provides large amounts of vitamin A; with the Three Sisters, farmers harvest about the same amount of energy as from maize monoculture, but get more protein yield from the inter-planted bean and pumpkin. Mt. Pleasant writes that this largely explains the value of the Three Sisters over monoculture cropping, as the system yields large amounts of energy, and at the same time increases protein yields; this polyculture cropping system yielded more food and supported more people per hectare compared to monocultures of the individual crops or mixtures of monocultures.[5]


Scholars Mt. Pleasant and Burt reproduced Iroquoian methods of cultivation with Iroquoian varieties of maize at several locations in New York. They reported yields of 22 to 76 bushels of maize (550 to 1,930 kg) per acre. Soil fertility and weather were the main determinants of yield.[14] Mt. Pleasant also questioned the conventional wisdom that the Iroquois practiced slash-and-burn agriculture, abandoning fields when the soil was depleted of nutrients after several years of farming, but instead claimed that Iroquoian no-till farming techniques preserved soil fertility.[15] In a similar experiment to reproduce Native American agricultural practices in Minnesota, Munson-Scullin and Scullin reported that maize yields declined year by year, from 40 bushels (1,100 kg) to 30 bushels (820 kg) to 25 bushels (550 kg) the third year.[16]

Other scholars have estimated lower average yields of maize. Hart and Feranec estimated the yield of Huron agriculture at 8 to 22 bushels (200 to 560 kg) per acre, the higher yields coming from newly cultivated land. The Huron lived in Ontario near the northern limit of where agriculture was feasible and had less fertile soils than many other regions. Nevertheless, they produced surpluses for trading with nearby non-agricultural peoples.[17] Bruce Trigger estimates that the Hurons required .4 acres (0.16 ha) to .8 acres (0.32 ha) of land under cultivation per capita for their subsistence with more cultivated land required for trade.[18] Sissel Schroeder estimates that the average yield of Native American farms in the 19th century was 18.9 bushels per acre (480 kg), but opines that pre-historic yields might have been as low as 10 bushels per acre (255 kg).[19] As the Iroquois and other Native Americans did not plow their land, Mt. Pleasant and Burt concluded that their lands retained more organic matter and thus were higher in yields of maize than early Euro-American farms in North America.[20]

Society and culture

Further information: Domestication

Maize, beans, and squash, whether grown individually or together, have a very long history in the Americas.[5] The process to develop this agricultural knowledge took place over 5,000–6,500 years. Squash was domesticated first, with maize second and beans third.[21][22] Squash was first domesticated some 8,000–10,000 years ago.[23][24]

Cahokian, Mississippian and Muscogee culture

From 800 AD, Three Sisters crop organization was used in the largest Native American city north of the Rio Grande known as Cahokia, located in the Mississippi floodplain to the east of modern St. Louis, Missouri. It spanned over 13 km2 and supported populations of at least thousands.[25] Cahokia was notable for its delineated community zones, including those for administration, several residential areas, and a large agricultural complex. [25] Domesticated squash, gourds, and maize were initially grown alongside wild beans; domesticated beans were not grown at Cahokia until 1250.[26] The cultivation of the Three Sisters crops by Cahokian residents produced a food surplus large enough to support Cahokia's expanded population, as well as further cultures throughout the extended Mississippi River system such as those of the Mississippian and Muscogee.[25]

There is evidence that Cahokia held at least one great feast around 1050-1100 AD. The food served at these gatherings included, alongside a variety of other plants and animals, several domesticated squash varieties, maize, and wild beans.[26] Food that needed to be processed, like cornmeal, would commonly be prepared at the feast site alongside non-food items that gave the feasts ritual or ceremonial importance.[26]

Eventual overuse of the environment in the areas surrounding Cahokia began to degrade the land. As the surrounding woodlands were cleared through overuse, runoff frequently flooded the crop fields throughout the growing season, limiting the ability to grow the squash, maize, and corn Cahokia subsisted upon.[25] By c. 1350, the Cahokia site had been mostly abandoned and the large population dispersed, though the Mississippian and Muscogee cultures continued to thrive until c. 1600, when contact with Spanish explorers brought Eurasian diseases, death, and cultural collapse.[25]

Haudenosaunee culture

Sign with raised letters reading, "Grain Pits. These pits are remains of community storage cellars for corn, beans and squash. Used by the Iroquois Indians. State Education Department 1935"
Historic marker in Madison County, New York

In the Handbook of North American Indians, the Three Sisters are called the "foundation of (Iroquois) subsistence", allowing the Haudenosaunee or Iroquois to develop the institutions of sedentary life.[27] The Three Sisters appear prominently in Haudenosaunee oral traditions and ceremonies, such as the creation story and the thanksgiving address.[4] Researchers in the early 20th century described more than a dozen varieties of maize and similar numbers of bean varieties, as well as many types of squash, such as pumpkin and winter squash, grown in Haudenosaunee communities. The first academic description of the Three Sisters cropping system in 1910 reported that the Iroquois preferred to plant the three crops together, since it took less time and effort than planting them individually, and because they believed the plants were "guarded by three inseparable spirits and would not thrive apart".[5]

Among the Haudenosaunee, women were responsible for cultivation and distribution of the three crops, which raised their social status. Male roles traditionally included extended periods of travel, such as for hunting expeditions, diplomatic missions, or military raids. Men took part in the initial preparation for the planting of the Three Sisters by clearing the planting ground, after which groups of related women, working communally, performed the planting, weeding, and harvesting.[28] Based on archaeological findings, paleobotanist John Hart concludes that the Haudenosaunee began growing the three crops as a polyculture sometime after 700 BP.[5] The Haudenosaunee frequently traded their crops, so the need for each crop could vary substantially from year to year. Jane Mt. Pleasant surmises that the Haudenosaunee may have typically inter-planted the three crops, but they could also have planted monocultures of the individual crops to meet specific needs.[5]

Maya culture

Further information: Maya cuisine

The Maya diet focused on the Three Sisters. Maize was the central component of the diet of the ancient Maya and figured prominently in Maya mythology and ideology. Archaeological evidence suggests that Chapalote-Nal-Tel was the dominant maize species, though it is likely others were being exploited also.[29]

See also


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  2. ^ Sempat Assadourian, Carlos (1992). "The Colonial Economy: The Transfer of the European System of Production to New Spain and Peru". Journal of Latin American Studies. 24 (Quincentenary Supplement): 62. ISSN 0022-216X. JSTOR 156945.
  3. ^ a b c d e f Putnam, A. R.; Duke, W. B. (1978). "Allelopathy in Agroecosystems". Annual Review of Phytopathology. 16 (1): 431–451. doi:10.1146/ ISSN 0066-4286.
  4. ^ a b c d e Mt. Pleasant, Jane (2006). "The science behind the Three Sisters mound system: An agronomic assessment of an indigenous agricultural system in the northeast". In Staller, John E.; Tykot, Robert H.; Benz, Bruce F. (eds.). Histories of Maize: Multidisciplinary Approaches to the Prehistory, Linguistics, Biogeography, Domestication, and Evolution of Maize. Amsterdam: Academic Press. pp. 529–537. ISBN 978-0-1236-9364-8.
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  8. ^ Sauer, Carl O. (1969). Agricultural origins and dispersals: the domestication of animals and foodstuffs (2nd ed.). Cambridge, Mass.: M.I.T. Press. pp. 64–66. OCLC 3917.
  9. ^ Mann, Charles (2005). 1491: New Revelations of the Americas Before Columbus. New York: Vintage Books. pp. 220–221. ISBN 978-1-4000-3205-1.
  10. ^ Hemenway, Toby (2000). Gaia's Garden: A Guide to Home-Scale Permaculture. White River Junction, Vt.: Chelsea Green Publishing. p. 149. ISBN 978-1-890132-52-1.
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    Cited in: Mt. Pleasant (2016), p. 87.
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  15. ^ Mt. Pleasant, Jane (2011). "The Paradox of Plows and Productivity". Agricultural History. 85 (4): 470. doi:10.3098/ah.2011.85.4.460. ISSN 1533-8290. JSTOR 10.3098/ah.2011.85.4.460. PMID 22180940.
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  17. ^ Hart, John P.; Feranec, Robert S. (2020). "Using Maize values to assess soil fertility in fifteenth and sixteenth and Iroquoian agricultural fields". PLOS ONE. 15 (4): e0230952. doi:10.1371/journal.pone.0230952. ISSN 1932-6203. PMC 7141618. PMID 32267852.
  18. ^ Trigger, Bruce Graham (1963). "Settlement as an Aspect of Iroquoian Adaptation at the Time of Conquest". American Anthropologist. 65 (1): 90–93. doi:10.1525/aa.1963.65.1.02a00070. ISSN 0002-7294.
  19. ^ Schroeder, Sissel (1999). "Maize Productivity in the Eastern Woodlands and Great Plains of North America". American Antiquity. 64 (2): 499–516. doi:10.2307/2694148. ISSN 2325-5064. JSTOR 2694148. S2CID 164003793.
  20. ^ Mt. Pleasant & Burt 2010, p. 62.
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Further reading