Three Sisters (agriculture)

The Three Sisters (Spanish: tres hermanas) are the three main agricultural crops of various indigenous peoples of Central and North America. The crops are squash, maize, and climbing beans (typically tepary beans or common beans). Traditionally, several Native American groups also planted sunflowers on the north edges of their gardens as a "fourth sister". 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 approximately 10,000 years ago, 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

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". In Indigenous American companion planting, maize (Zea mays), beans (wild beans and vetches 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. In the northeastern U.S., this practice increases soil temperature in the mound and improves drainage, both of which benefit maize planted in spring. In Haudenosaunee or 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. A modern experiment found that the Haudenosaunee Three Sisters polyculture provided both more energy and more protein than any local monoculture. The three crops benefit by being grown together. 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. The prickly hairs of some squash varieties deter pests, such as deer and raccoons. Although this synergy had been traditionally reputed among American cultures, scientific confirmation has arrived only much more recently. 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. 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. Pronin et al. 1972 find increased productivity and root exudate in both crops when combining faba beans with maize, and even more so in soils with preexisting high nitrogen fixing microorganism activity.

Indigenous peoples throughout North America cultivated different varieties of the Three Sisters, adapted to varying local environments. The milpas of Mesoamerica are farms or gardens that employ companion planting on a larger scale. 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", the Rocky Mountain beeplant, which attracts bees to help pollinate the beans and squash. The Three Sisters crop model was widely used by a number of First Nations in the Great Lakes–St. Lawrence Lowlands region.

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