The Three Sisters Planting Guide

The 'Three Sisters System' is quite well known in the veg growing world. It originated in Latin America and is still used there today as a traditional system of companion planting that benefits each of the three plants, or sisters. The sisters are sweet corn, squash and beans. The idea behind it is that the squash with its big leaves covers the ground and prevents weeds from growing, the beans nurture the soil by extracting nitrogen from the air and releasing it into the ground, and the sweet corn make great climbing poles for the beans. This is companion planting at it's best, the plants nurture each other, reduce weeds and support each other's growth. Traditionally the three crops would have been harvested at around the same time and planting the three crops in the same field also means you get the highest possible yield for the amount of land being used. It is no wonder that this brilliant high-yield but low labour system was invented by peasants whose lives after all depended on the success of their crops.

At Helen's Bay Community Garden we planted the three sisters in our polytunnel. We customised the rules a bit in our case, and that is really what anybody should do when considering the three sisters system. You can use the concept of the system but use slightly different plants, either in the same family or with the same purpose. Instead of using squash or pumpkins we planted different varieties of courgette that are giving us a continuous crop of multi-coloured courgettes every week. Moreover, we planted runner beans, mangetout and french beans in the same row as the sweet corn so that the plants would climb up the corn. These three varities of the legume family will give us a varied crop and they all have different coloured flowers which makes the whole system even prettier. The sweet corn has been planted in rows and the squash is planted in the middle. This gives us one long and very productive bed. The reason we planted the three sisters in the polytunnel was because we started our corn and squash plants a bit late and the added heat and cover of the polytunnel just guarantees a better chance of success, particularly in Northern Ireland where the climate isn't very dependable. 

As you can see in the picture, the beans really do climb up the sweet corn! We did add a few bamboo canes though just to ensure that there is enough space for all the beans and mangetout to climb without cramping each other.

Our verdict is that this system has definitely been a success and that it looks very attractive in a polytunnel. The only thing is it has to be watered regularly, especially in warm weather, for the plants to produce good crops. We will probably try the system again next year, but outisde this time, and we urge everyone to give the three sisters a go!