I was first introduced to “The Three Sisters” last summer while assisting at Root Camp back in the UK. I met them once more a month ago when helping to shovel compost and clear weeds for Edible Schoolyards NYC.
“Who are these mysterious ladies?!”, I hear you cry. Beans, maize and squash. Oh the glamour.
So The Three Sisters is a planting method with its roots in indigenous Mesoamerican practices – you’ll notice that domesticated maize and squash (including pumpkins and courgette/zucchini) are uniquely native to North America, while different varieties of “beans” are found all over the world. The Three Sisters is a beautiful example of “mutualistic” or “companion” planting, where the properties of one plant benefits or complements those of another (a simple example would be planting lots of flowers in the vicinity of crops which need insect pollinators). Let me briefly describe the plants in question.
Maize is a tall plant,
and there are some varieties which can grow up to 12 metres (amaizing). This characteristic makes it ideal for high-density monoculture planting, as can be seen from the photos. The plant is fairly intolerant of dry or nutrient-poor soil, and the roots are surprisingly shallow considering its height.
The kinds of beans in question are in the class of green or flageolet- or haricot-type beans.
As can be seen from the last image, these guys are climbers – they send out little anchoring tendrils to fasten onto more robust structures in a kind of trapeas act. This means they don’t have to waste energy making hard or woody stems.
Crucially, they are legumes, which as you may remember from secondary-school biology, means they host “nitrogen-fixing” bacteria in their roots. These bacteria extract the fairly inert nitrogen gas which comprises 80% of the air, and turns it into chemically reactive forms such as ammonia, which can in turn be converted into the nitrates so vital for plants.
Finally, squash plants are more low-lying than the other two. They prefer to spread out horizontally rather than growing vertically upwards.
To really understand what motivates squash to grow like this, you have to photosympathise.
Anyway, you’ll already have worked out why these three go so well together.
The maize provides support for the beans; the beans enrich the soil; and the big squash leaves protect the soil from drying out, while simultaneously mopping up all the sunlight that wasn’t caught by the taller plants. There are other benefits too from the perspective of pest control which I won’t go into; but already it’s ingenious. Can you beleaf it?
If only all sisterhood was so harmonious.
We should bear in mind that most of our food is produced using industrial farming methods, which promote the use of genetically similar monocultures whose planting can be pushed to high densities and whose harvesting is easy to mechanise. The viability of such an approach is heavily dependent on the ready availability and low monetary cost of artificial fertilisers and pesticides. This being the case, industrial farming has greatly enhanced our ability to produce cheap and abundant food, with clear societal benefits.
Yet our growing understanding of the hidden costs of the current system – disease vulnerability, water pollution, greenhouse gas emissions, food security, corporatisation of food supply, social justice, and more – has for some decades been fuelling a renewed popular interest in alternatives, of which The Three Sisters is a wonderful example.