Trivia time. The corn benefits from nitrogen fixed by the beans. The corn benefits from the pumpkins because raccoons don’t like walking through the pumpkin leaves to get to the corn. If planted properly, the pumpkins sprawl on the ground pretty much covering the ground with leaves while the beans and corn stand above where they can get plenty of light.
Also, most modern pumpkins won’t work with a 3-sisters garden. They either grow too large, grow over everything around them including the corn, or don’t sprawl enough to cover the ground. One that I have used is Long Pie which you can find at a few vendors including Sandhill Preservation.
Beans planted in 3-sisters should be a fairly fast growing type. I’ve used Turkey Craw to some effect. Plant the corn and wait until it is about a foot tall, then plant the beans. If planted too early, the beans will overwhelm the corn.
You can plant beans on every other corn mound and pumpkins on every 3rd mound. I used 4 feet spacing between mounds but they can be closer in some climates and should be further apart where low rainfall limits production.
