The banana circle has become as iconic in permaculture design as the herb spiral and chicken tractor.
A banana circle is simply a circular hole about 2m in diameter and up to 1m deep. The earth removed from the hole is mounded around the outside and used to grow plants. The pit in the middle is used as a wet composting area. The breakdown of organic material in the central pit provides nutrition for the plants growing around the perimeter. If the circle is positioned where runoff is being utilised, a lead-in drain or swales can also be incorporated into the design to trap the water and direct it to the banana circle.
As bananas like lots of water and are heavy feeders, a banana circle is a great way to deal with a problem boggy area as well as a place to dispose of your compost and kitchen scraps. Waste water can also be piped into the centre of the circle. Some designs even have an outdoor shower over the top of the banana circle.
A typical banana circle mound can support five to seven bananas and they will thrive off the abundant cycling of organic material as well as the moisture from the wastewater. From there, a myriad of plants can be grown on the outside mound. Typically, the plants used are banana, papaya, taro, cassava, lemongrass and sweet potato. The tall growing plants (banana, papaya) will provide sun protection, while the rest of the plants will provide ground cover.
As the bananas produce young plants (pups), one pup is chosen to replace the parent plant, and for all of the bananas in the circle a pup is picked that is on the same side of each plant (ie a pup to the left side of every banana in the circle). In this way, the new plants will “walk” around the circle in either a clockwise or anti-clockwise direction and will not move in towards each other.
Although the banana circle is traditionally a tropical design element, they can be successful in warm temperate climates too. To achieve this, it may help to create a microclimate using thermal mass walls, suntrap designs, ponds, etc. If tropical plants in your banana circle do not appeal to you then you can use the same system for other plants – a fruit tree circle perhaps. Plants which are heavy feeders will love the easy access to the nutrient rich compost heap (citrus and passionfruit for example). If you do decide on planting something other than bananas however, you will need to consider the water requirements of your chosen plants – in this instance you may not want to plant in a boggy area or run your waste water into such a system.
Now run outside and create your oasis!