That was the name certain native American peoples gave to companion plantings of beans, squash and sweetcorn. I'm not sure if it was those of South, Central or North, but I understand the combination was used by agrarian cultures all over the Americas. I've been meaning to set up a bed of them for a while, because I'm curious, I like all three of those vegetables, I'm keen to maximise the space in raised beds, and when I learned they were called the Three Sisters it appealed to me especially as I am one of three sisters myself, though I can't make up my mind which of the three I'd like to be and which most resemble my two sisters.
The virtue of the combination is that the sweetcorn supports the beans, which in turn enrich the soil with nitrogen for the benefit of the corn. While those two are reaching for the sky, the squash plants use the ground below, and their leaves and vines spread and keep down the weeds and keep it cool and moist.
It's worked to a point, but in fact I overcrowded the bed rather too much; when it looked like this
in June, after the rabbits had nibbled the tops off the sweetcorn, I couldn't believe that a couple of months later it would look like this:
I don't know how many years of observing the actions of nature it will take me fully to grasp the reality of them.
However, it will yield something, and the evening and sometimes morning plod down there bearing watering cans - the hose doesn't reach - is satisfying more than onerous. I planted Kelvedon sweetcorn, green courgettes ( aka zucchini, I forget which variety), a special kind of butternut squash called 'Sprinter' which is supposed to be better suited to northern climes than the regular one, and pea beans, a flat French-type bean which you allow to dry in the pods to harvest the little round skewbald seeds for winter soups and stews, all from the organic gardening catalogue. The germination rate for the courgettes was rubbish, but three surviving plants still give us more courgettes than we can use, the Sprinters may not be exactly sprinting but they are growing at their own pace, unfortunately though they are covered in flower buds the vast majority of these are male and won't bear fruit, but their are a few small green gourds coming along. The sweetcorn is bringing forth cobs; they look a bit small but size isn't everything. The beans seem to be doing their own thing quite happily.
But whatever, I'm enjoying the look of them, the different leaf shapes and splashes of flowering and the emblems of the fruit, so if the only significant harvest is photos, then so be it.