Three Sisters intercropping
By the time Europeans arrived, Phaseolus vulgaris beans were cultivated throughout the New World, in North America as well as Central and South America. They were widely used in combination with two other New World crops (corn, Zea mays, and squashes or pumpkins, Cucurbita species) in a combination often referred to as the Three Sisters, in which the plants grow in mutually beneficial ways (providing nutrients, structure, and shade from competitors for each other), and providing complementary food sources for complete human nutrition, because the squash and beans supply amino acids not found in corn, including lysine and tryptophan, but needed for a complete protein.
(Hedrick 1919, Wikipedia 2012.)
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