I've experimented with Three Sisters a couple of times when I had an allotment , it can be a very useful way to maximise Yield from a smaller patch of land. I found in the UK its important to start the Corn off as early as you can as potentially the beans will over run the corn strangling it. So the Three Sisters method involves growing three Plants in a single area to maximise growth , the First Plant ( Sweet Corn ) will add as a structure for Climbing beans to climb up , amid the plants at ground level you plant Squash's with have a prolific growth pattern which acts as a natural weed suppressant and mulch. If you've only a small area its worth trying as an experiment and can give big results. https://www.victoriananursery.co.uk..._And_Squashes_Using_The_Three_Sisters_Method/ Its potentially possible i would think to grow some sort of Tuber plant along with the Three Sisters - Possibly Potato or Oca. Again its all down to timing and know when to take the harvest.