Every so often on my wanderings around the net, I have come across these photos of lovely healthy plants being grown in the trunks of banana plants. Of course, once a banana has flowered and produced a crop, the parent plant dies back and is succeeded by two daughter plants. The dead parent plant is cut back and composted or whatever, but in this idea it is turned on its side, laid on the ground, holes dug into it and it is planted out with veg seedlings. On the face of it, it seems to be a good idea, making use of waste materials to grow more food, with the banana trunk eventually decomposing completely to enrich the soil.
There is also other benefits. Under certain (unexplained) circumstances the banana trunk contains sufficient water to ensure the plants being grown do not go dry. Certainly I have cut down many a banana trunk which has fruited and the amount of water that drains out is incredible. Also, being organic material, it will break down over time and provide nutrients for the growing seedling.
Concerns
I do have a couple of concerns with this scenario. The first one is that even though the banana is chock full of water, would it be enough? Also, when the banana starts to break down, the nature of the beast is that initially nitrogen would be locked up and it would take a while to be available to the seedlings.
Process
Well I had a banana trunk so I thought I would give it a go! The trunk I chose to use was the biggest I had at that point, with a diameter narrowing from 120mm at the wide end down to 80mm at the other end. I cut it to 1500mm long.
To cut holes into the trunk I decided to use my 70mm hole saw, a knife and a 30mm spade bit, I thought the spade bit was a bit small but tried it anyway. They all worked pretty well in making the holes.
Once the hole saw had done its evil work to about 80% of the way through the banana trunk I had to dig the cut layers from centre out to make the hole. The spade bit just dug its way through the banana quickly and effectively. The knife was a bit more difficult, but not much. I cut the holes in about 300mm apart, because it is a nice round number.
I planted the seedlings I had raised using my potting/seedling mix (! Part course sand, 2 parts worm castings, 3 parts cocopeat) and planted them directly into the holes. I planted a couple of lettuces, a tomato and a cucumber.
I then placed the planted out banana against the southern fence on one of the vege patches so that as it decayed it would rot down into the soil. At the same time, I planted a lettuce into the soil as per my normal process, about 400mm away from the banana trunk.
Results
It has been 5 weeks since the plant went into the banana trunk and the lettuce in the ground is doing much better than the one in the trunk, (see pic below). I am not sure why, but it could be any one of a number of factors, possibly even nitrogen lock up. Anyway, that’s what we have.
Unfortunately, as I suspected, the 30mm holes were just not big enough and the veggies in them did not do very well. It also became obvious that the amount of water in the banana was only enough to maintain the seedlings for a couple of days and regular watering would be required. Perhaps if the trunk were larger in diameter, I don’t know. One the reference I found said that the plants would not need to be watered in certain circumstances, and I suspect the circumstances would be daily rain!
I will continue to monitor and see how things go. My two concerns seem to have been borne out, at least to an extent. We’ll see how things go!
