Maize, beans and squash grown together feed more people than any of them grown alone.
Indigenous farmers across North and Central America planted the Three Sisters together. Maize gives the beans a pole to climb, beans enrich the soil with nitrogen, and squash leaves shade out weeds. Modern trials suggest the combination yields more protein per field than growing any one crop alone.
The three crops were domesticated in Mesoamerica, squash first about 10,000 years ago, then maize, then beans, over some 5,000 to 6,500 years. Grown together, they became the basis of agriculture across much of the continent. Sixteenth-century European accounts describe highly productive Three Sisters farming from Florida to Ontario, feeding communities and supplying trade. Some peoples added a fourth sister: sunflowers on the north edge of the garden, or, among the Tewa of the Southwest, Rocky Mountain beeplant to draw pollinators.
The classic method builds mounds of soil each year, planting maize and beans together in them and squash between. Each crop helps the others. The maize stalk is a trellis for the beans. The beans fix nitrogen in their root nodules and their twining vines steady the maize against wind. The broad squash leaves shade the soil, keeping it moist and suppressing weeds, and prickly varieties deter animals such as raccoons. In the north-east, the mounds also warm and drain the soil for spring-planted maize.
This synergy was known to Indigenous growers long before scientists confirmed it. Soviet research in the early 1970s found that many legumes boost maize growth and yield. More recently the agronomist Jane Mt. Pleasant showed that Haudenosaunee (Iroquois) Three Sisters plantings produce about as much energy as maize alone but more protein, which is why the system supported more people per hectare. Together the three crops supply all nine essential amino acids, and squash adds vitamin A.
Mt. Pleasant also challenged the old assumption that such farmers exhausted the soil and moved on. Haudenosaunee fields were not ploughed, which preserved organic matter and limited erosion, and in her reconstructions yields reached 1.4 to 4.8 tonnes of maize per hectare. Other scholars estimate lower yields for some groups, so the debate continues, but the lesson for gardeners is enduring.
Source: Wikipedia — Three Sisters (agriculture) · Text summarised from Wikipedia (CC BY-SA 4.0)
