Underneath the soil the balancing act continues. The beans are legumes - famous for their ability to reduce nitrogen to nitrates by using their root nodules filled with nitrogen fixing bacteria. Corn is notorious for sucking nitrates from soil at a high rate. In the context of large scale farming, corporations get around this by dumping tons of nitrate fertilizers on the corn fields. To fix nitrogen artificially fertilizer producers need to use copious amounts of fossil fuels. This demonstrates that our current food supply relies on ever-evaporating cheap fossil fuels. Another pressing reason to remember and respect the wisdom of the three sisters.
The origin of this wisdom is not a university laboratory but the pre-Columbian fields of present day New York State. The Iroquois or Ho-de-no-sau-nee stumbled upon this beautiful triumvirate sometime during the millenia they lived and played there. So central was this horticultural combination to their sustenance that it became intertwined with their spiritual world-view.
Lewis Henry Morgan writes in League of the Iroquois (First published 1851).
"These plants were regarded as a special gift of Ha-wen-ne-yu (The Great Spirit); and they believed that the care of each was entrusted, for the welfare of the Indian, to a separate Spirit. They are supposed to have the form of beautiful females, to be very fond of each other, and to delight to dwell together. This last belief is illustrated by the natural adaptation of the plants themselves to grow up together in the same field, and perhaps from the same hill. Their apparel was made of the leaves of their respective plants; and in the growing season they were believed to visit the fields, and dwell among them. This triad is known under the name of De-o-ha-ko, which signifies Our Life, or Our Supporters. They are never mentioned separately, except by description, as they have no individual names."
Depending on where you live the time to plant these varies but on average the span between April 20th and mid May marks the optimal planting window. As an added bonus cultivating a garden in your yard or containers in your apartment with your children boosts their veggie intake and physical activity.
For a much more in-depth look at the practical aspects of cultivating the three sisters see this article by the homesteader John Vivian.
Tom Vilsack can't be all bad if he appreciates this wisdom.
HERMANN, J., PARKER, S., BROWN, B., SIEWE, Y., DENNEY, B., & WALKER, S. (2006). After-School Gardening Improves Children’s Reported Vegetable Intake and Physical Activity Journal of Nutrition Education and Behavior, 38 (3), 201-202 DOI: 10.1016/j.jneb.2006.02.002