Before humans began practicing agriculture about 12,000 years ago, beans, squash, and teosinte grew together in the wild near Oaxaca, Mexico. As indigenous people transitioned from a hunter-gatherer culture to an agricultural one — during a span of about 5,000 years — they slowly abandoned their nomadic lifestyle and domesticated these wild plants for a more stable food supply.
Ancient Agriculture: The Milpa
Mesoamerican farmers imitated nature by growing crops together in a milpa, which was a field of maize, beans, squash, avocados, jicama, and other wild plants that they’d tamed. Milpas were traditionally farmed for a few years and then allowed to go fallow for better production. The symbiotic relationships among the plants in the milpa created a healthy and richly diverse ecosystem. The plants supported one another, offered habitat for wildlife, and complemented each other nutritionally, providing a balanced diet. In his book 1491, Charles Mann states that milpas have been continuously planted for about 4,000 years.
Through extensive trade routes, this farming system spread across Mexico. Gradually, the milpa made its way to the pueblos of the Southwest, extended farther north to the Great Lakes region, and migrated finally to northeast North America. Some of the tropical plants of Mexico’s milpas weren’t adaptable to the colder regions, but maize, beans, and squash were successfully bred for the shorter growing season and vital winter storage.
Although most native people grew maize, beans, and squash together, the Iroquois named the system Three Sisters, or Deohako. Each nation had its own legend about these plants, the common thread being that the sisters were very close and stronger together than they were apart, which helped the people survive.
In the field, towering maize stalks provided support for vining beans, which helped tie the stalks together for added stability. Beans also pulled nitrogen from the air and, through decomposition, transferred it to the soil, making it available later to the maize and squash, both of which are heavy nitrogen users. The broad, low-lying squash plants acted as mulch to suppress weeds, conserve moisture, and keep the soil cool. Plus, their prickly stems deterred predators.
Nutrition for the Earth and the Farmers
The biological diversity of maize, beans, and squash grown together create a polyculture. Each plant utilizes different nutrients in the soil and then returns those nutrients to the soil as they decompose. The root systems of these three crops are of varying sizes and depths, which helps to break up the soil, and because each crop is a different height, they’re each able to capture available light from various angles. Diversity provides protection from devastation, too. One pest or disease wouldn’t wipe out an entire field, and a harvest of some sort is nearly guaranteed.
Maize, beans, and squash also complement one another for a nutritious and well-balanced diet. For example, the combination of maize and beans creates a complete protein. Squash is full of vitamins and minerals that the maize and beans both lack, and squash seeds provide oil and protein. Maize and squash are also both high in calories, which help sustain energy.
The benefits of growing these three crops together are clear to modern soil scientists and nutritionists, although at the time there was no scientific knowledge behind this sophisticated planting method. It was simply the result of Mesoamerican farmers being keenly aware of their environment and experimenting for thousands of years to grow the hardiest and most nutritious crops.
Growing the Three Sisters
Eastern and northern nations grew the Three Sisters in rows of mounds about 4 feet apart on center. In regions with regular rainfall and cool springs, the mounds were warm, dry microclimates in the field. In some locales, the maize and beans were planted in the mounds, and the squash grew between the rows. Where fish was abundant, carcasses were placed in the mounds as fertilizer. At the end of the growing season, the finished plant remnants were incorporated directly into the soil for added fertility.
The Tarahumara of northwestern Mexico, on the other hand, planted a block of several rows of corn and surrounded it with beans. They planted squash along one side of the field.
In the arid Southwest, the Three Sisters weren’t always planted side by side, either. According to the nonprofit Native Seeds/SEARCH, the Hopi and Navajo planted each crop in a separate part of the field and used wide spacing to take advantage of scant rainfall. Farmers in this region sometimes grew sunflowers and amaranth, which were also important food sources, along with the Three Sisters. The Hopi grew wild cleome (Cleome serrulata, or Rocky Mountain bee plant) to attract pollinators for the squash.
Post European Contact
After Columbus’ arrival, colonizers took some native seeds across the Atlantic Ocean to Europe. There, maize, beans, and squash were bred and developed separately, along with many other foods. European settlers returned to North America with new cultivars that had developed characteristics suitable to their European environments and were labeled with European names.
As Europeans moved west, these crops spread west, too, and some have become today’s heirlooms. Others — the most economically important — have been hybridized and engineered for almost 100 years, making the seeds impossible to save true to form and resulting in an increased loss of seed diversity. And yet, some of the original, or purely Native American, cultivars remain, thanks to the efforts of the strong cultures that continue to nurture them and others who have recognized the importance of these cultivars over the centuries.
Continuing the Ancient Tradition
The milpa was the first deliberate companion planting system in the Western Hemisphere, and maize, beans, and squash were the hardiest and most adaptable of those crops for northern climates. Like all of our food, though, they first grew in the wild thousands of years ago.
Today, with the rising popularity of organic gardening and an increasing awareness of indigenous agricultural history, the Three Sisters system is returning to backyard gardens. A handful of native seed cultivars are available commercially, but the best seed choices are those grown locally because they’ve adapted to the soils and weather of the region. To keep the Three Sisters tradition going, and to honor the ancient farmers of Mesoamerica, try growing heirloom squash, beans, and maize together, and save seeds from the hardiest, tastiest, and most beautiful open-pollinated plants in your garden.
Nan Fischer is the founder of the Taos Seed Exchange, a free seed-swapping service offered to home gardeners in Taos County, New Mexico. She has a degree in horticulture and has used her knowledge to nurture plants for more than 40 years.
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I wanted to plant the traditional three sisters, corn bean & squash. Was wondering about timing, which to plant first. The suggestion below seems to indicate the corn should be planted first, waiting until it reaches 6" or so in height, followed by the beans ( I have an antique variety, Hidasta Red I hope to grow). When should the squash go in & where in the plant bed. Any suggestions?
We have successfully co-planted corn with pinto and great northern beans, with squash in nearby mounds, for many years. We have also co-planted these beans with tomatoes. In each case, we use mounded rows, form a valley in the middle with a flat shovel, place compost in the valley, then plant the tomato seedlings (between 6ā-10ā tall) 18ā apart, and then place four beans on the cardinal points around the tomato plant, as well as on four inch centers between the plants. Same with corn, but wait to plant the beans until after the corn has germinated to a height of six inches. All of the species do well, with no pesticides, just a daily scan for bugs, which are dispatched manually with a pair of hemistats. Pick the tomatoes or corn first (in north florida in late May, early June) then let the bean pods dry in the field, but be sure to pick them before the summer rains, or they might begin to sprout on the vine if they get too wet. We grew enough beans and tomatoes last year this way that we do not need to plant them again until next year. They seem to love growing together.