Banana Pit

When we moved up to Queensland I knew that one of the first fruit crops that I wanted to grow was bananas. As bananas have high water and nutrient requirements, that limited the number of places to locate them, as at the time we did not have the pond created or the associated irrigation pump setup. So there were two main choices, one location by the shed and the other location below the treated effluent sub-surface irrigation. The shed location also meant that I could use water from our laundry to aid with irrigation of the bananas (we use Aware laundry powder from Planet Ark), so this ended up being the spot selected.

Through my research on growing the plants, I was particularly drawn to a banana circle/pit design. A banana pit was the best choice for the shed location, as it was mostly exposed decomposed granite (deco) sub-soil. Thus very little would grow in it. I knew I wanted to have four different banana plants growing which dictated a minimum 1.6 m spacing. Therefore I figured a 3.5 m square pit would do the job. While most permaculture designs use a circle, I liked the square shape as it meant I could plant other things in the corners of the square (as the bananas are planted in the middle of each side of the square). The pit needed to be about 0.5m deep with the centre of the pit being even deeper for greater water storage and compost collection.

So with location and design sorted out, it was time to do the hard work. My tools and equipment were a shovel, mattock, and wheelbarrow.  About three days later, the hole was excavated, and I needed a holiday. As the material from the pit was not suitable for growing much on its own, I then proceeded to do mass composting within the pit. Using repeated green grass, dry grass, manure, and deco layers, I proceeded to create the soil needed to sustain my future bananas. While I had the grass and deco material covered, my limiting resource was the manure. Thankfully neighbours (stock) were able to supply this over the next few months.

Whilst the compost was being made, I was also doing research on what type of bananas to grow. In Queensland, you need a free permit to grow bananas up to 10 banana plants. Moreover only certain types of bananas are permitted to be grown by the home gardener. The only permitted varieties are Ladyfinger, Blue Java, Ducasse, Goldfinger, Bluggoe (plantain or cooking banana), Kluai Namwa Khom (Dwarf Ducasse), and Pisang Ceylan. I selected:

- Lady Finger, although relatively common, as it is a nice tasting banana and the plant is drought hardy.

- Blue Java as it is know as the ice cream banana (and I love ice cream). As it turns out, this banana makes the best custard too.

- Goldfinger as it is supposed to be a delicious banana (still have not tasted this one yet). This banana can also be used for cooking when green.

- Dwarf Ducasse as it is a small size and has a sweet pleasant flavour. This banana can also be used for cooking when green.

I passed on the Ducasse as I chose the dwarf form, Bluggoe was rejected as some of my choices can also be used for cooking, and Pisang Ceylan wasn't selected as I only wanted to fit four types of bananas in my pit (otherwise I would have chosen this variety as well, and may still do so in the future).

While I would like to think with my up front research that I do not make mistakes, sadly this is not the case. When the bananas arrived from the supplier Backyard Bananas (http://www.backyardbananas.com.au), I was quite keen to get them in the ground where they would grow at a furious pace. I had found out that with tissue culture bananas, it was best to plant them up to their neck in the ground; the neck on a banana plant is just below where the leaves start to branch out. The idea behind this technique is this it would reduce any issues with plant stability when they started suckering. Unfortunately if your "soil" is still too hot from the compost making process, then the use of this technique will quickly kill your banana plant as it did with my initial Lady Finger plant. I was fortunate enough to be able to rescue the Blue Java banana as it was not in the planting spot more than a day.

After allowing the composting process to truly cool down, I was able to get some of the plants back in the ground (I still had not acquired enough manure at this point to have filled in the planting area around the pit). I also started putting some sweet potato, pigeon pea, and ginger around the outside of the banana pit. However with some heavy rains around November of 2008, my banana pit was flooded causing some of the side plantings to become flooded. I had thought that the deco sub-soil would be fairly well draining, whereas the opposite turned out to be true. Deco holds water very well (including material with not much in the way of clay particles). So a design change was in order; I opened up the eastern side of the pit and made some trenches. This allowed water to flow into the pit when it was dry, but also allowed water to flow out when the pit water levels rise. This design has turned out to be extremely successful and I now have a 90mm pipe angled slightly down into the pit which is covered with soil.

Of the plantings I have had around the pit, some have worked out well, where others have been a failure. For instance, I would not recommend sweet potato as while it will form tubers, obtaining them means disturbance to the roots of the bananas. Moreover sweet potatoes like acidic soil, whereas bananas desire a neutral pH. However ginger, galangal, and turmeric which are all tuber harvested plants have fared very well. They do not mind the competition from the bananas and produce prolific crops. One does have to be mindful of the amount of sun with some of these plants, as such pigeon pea is a great mid-storey plant which will provide partial shade when a banana plant is removed after its fruit has been harvested. Pigeon pea is very hardy and can take full sun or partial shade conditions.

The middle of the banana pit has been progressively filled with organic material which breaks down to feed the banana plants. While this type of environment, being wet organic matter with little oxygen, can created an acidic environment, I have not found it to negatively impact the health of the plants. To help counteract acidity, I have used bones and lime at the bottom of the pit along with more lime as I build up the layers of material. The great thing about this setup is that it takes very little effort to throw palm fronds and other coarse material into the pit. Even old banana plants are left to decompose in the middle of the pit. So as a result of the initial compost making process, the high quantities of potassium in the decomposed granite, and the ongoing supply of organic material in the pit, I have not had to fertilise the banana plants with purchased products. The result so far has been healthy vigorous plants producing large bunches of bananas. I ensure that I regularly de-sucker the plants using a shovel. I have a baby, mother, grandmother, and sometimes great grandmother relationship. Therefore I only have one plant of each type producing fruit at one time. Although occasionally a daughter plant will produce a bunch while its mother's bunch is still maturing. I have been trialling having two plants of a single variety producing fruit at the same time so we will see what the results of this are.

To prevent the banana plants from falling over when they have a heavy bunch on, I use props made from Chinese Elms. These make a huge difference to the stability of the plant, although the prop will not always prevent a plant from falling over in high winds. Initially, banana bags were used quite a bit to protect the fruit. However I have found that a rodent liked the dry and wind free environment (it did not damage the fruit, but did damage the bag). I have also found that pests such as mealy bugs and scale prefer a bagged environment. So now I am trialling the use of no bags. So far the birds and bats are leaving them alone.

I have been very pleased with the ease at which bananas can be grown in SEQ so I recommend it to everyone in the club who does not mind doing minimal regular maintenance. You will certainly be rewarded with fruit, probably more than you can eat or freeze!

 

Authored by: 
Jason Spotswood