Native Americans from the Iroquois tribe devised the "three sisters" method of planting corn, pole beans, and squashes together for the vegetables' mutual benefit. The corn stalks become a trellis for the beans, which in return fix nitrogen in the soil and prevent those stalks from being blown over by strong winds. The prickly squash plants deter raccoons, keep down weeds and shade the soil so that it doesn't dry out, while the corn canopy provides them some protection from squash borers.