One thing I really enjoy at a permaculture garden is that you can litter without feeling guilty. Growing up in spick-and-span Singapore we have been taught since young to put litter only in the rubbish bin. Any piece of trash left on the concrete floor is an eyesore and has to be cleaned up by someone else. This is why it felt so liberating when I could throw my organic waste anywhere in the farm. In fact, my act of littering will be adding to the fertility of the soil and if I was lucky it might even be seeding a tree!
The banana circle is a simple yet effective design for permaculture in the tropics. It is basically a circular trench with bananas planted at the rim of the trench. All kinds of organic waste can be thrown into the circle, including dead leaves, garden prunings, kitchen waste, hay, rice husks, even short logs. Anything that will rot can be thrown in. As the organic matter breaks down, the hungry banana trees will readily suck up the nutrients and turn the waste into yummy bananas. The depression into the ground helps to retain moisture that the bananas love and also speed up decomposition.
You can substitute bananas with other nutrient hungry plants like papaya and pigeon pea. The trees that grow really big might not be suitable unless your circle is very big. On the inner edge of the rim you can plant wet-loving plants like taro and yam. On the top or outer edge of the rim you can plant dry-loving plants like lemongrass, tapioca, and sweet potato.
The banana circle can also be a grey water treatment system. You can direct your grey water (ie from kitchen sink, bathroom sink) into the banana circle and the water will be stored within the waste and into the soil. For the brave ones, you can even place a grid or platform of wood over the circle and turn the banana circle into a shower area or wash-up area. Just make sure you plant dense enough for privacy!
This website has good diagrams on how the banana circle looks like.
I have dug a few banana circles and it’s always a lot of fun. I typically stick to no-dig farming which is why constructing a banana circle gives me an opportunity to satisfy my digging crave! My first banana circle (seen below) was dug out over half a day until I hit the water table. Unfortunately I had to fill up the hole when we had to return the plot after a week…
We also dug a smaller banana circle at our Green Valley plot. This one was a little tricky because the banana trees were already planted in for a while before we dug the banana circle. There were definitely some tattered banana leaves. It has been working amazingly like a black hole. We have been throwing heaps of organic waste including soybean pulp, garden waste, grass weeds, and rotting bamboo. The dome keeps disappearing and the banana trees keep getting bigger and thicker.