Here's a photo of one of the successful new trees. The truck is about 5 foot tall, topped by a 2 foot long new leaf shoot, still tightly curled up. Yes, it's difficult to see in this lousy photo.
Here's a close up of the new leaf shoot. It will grow at least another foot before unfurling into a beautiful new banana leaf.
I've been getting some banana questions lately, so I'd like to take the time to give out more information on how I grow bananas in order to cover everyone's questions. Keep in mind that this is how I do it. I'm sure that there are other ways to be successful too.
When I plant new bananas, I bury the root base a good 8" deep. By that I mean that the top of the root area is 8 inches below the soil surface. They do just fine being planted this deep. They don't require this depth as they will often grow even if I had just laid them down on the soil surface, but then the tree wouldn't have good support. It would be in danger of blowing over in a brisk wind. Planting deeper gives them the opportunity of sending support roots deeper and under the lava chunks. Planting deep like this means that I don't usually need to support the young tree with stakes. But sometimes if the tradewinds are blowing strongly, I'll brace the tree for the first few weeks until it is solidly rooted. In addition, I usually remove most of the current roots before planting. The plant sends out new roots within a couple days, anchoring the tree within one to two weeks, depending upon the weather and soil moisture. That sounds brutal and bad to be removing the current roots, but the trees do just fine. The old roots die and rot away anyway, so by removing them I'm reducing the amount of rot that will build up around the root base.
I normally don't do any preparation on the hole before planting the young banana tree. No fertilizer, lime, compost, etc. I think the trees transplant better without the hole being prepped, BUT that's how it works for my own particular soil. Maybe if I were planting into lava rock, I'd do a different approach. After the tree appears to have taken, I will apply a generous layer of compost that includes livestock manures, around the tree, about 6' in circumference around the trunk. Because of my acidic condition, plus the fact that bananas require potassium, I will apply wood ashes. I'll work this in lightly with my tiller. That's about it for the next several months. After a few months I will need to mulch to control weeds, so I use compost (which includes livestock manures) for the mulching job, then top it with a light layer of grass clippings. I'll check the soil pH and add wood ashes as needed. From thence on, I'll just apply compost (with manure) or mulch as need to control weeds, retain moisture, and keep the soil covered. And keep an eye on the pH and wood ash applications. Why do I keep saying compost with manure? Because bananas appear to be big nitrogen feeders.
Another thing I'll sometimes do is dig a trench about 1-2 foot deep about 6' away from the trunk. If not a trench, then a hole. Why? To fill with organic material such as garbage, waste fruits, coffee waste pulp, dog poop, cat box cleanings, other manures, road kill, and whatever else I need to get rid of that will rot down. This all will eventually provide nutrients to the clump without destabilizing the soil that supports the heavy trucks. And it's a good use for things I don't wish to use in the other food gardens, such as the pet waste.
For the first few weeks I keep the soil around the newly planted bananas moist but not soaking wet. I take care not to let it dry out. Letting the soil get dry often results in transplanting failure. I'll check the baby trees daily, giving them a gallon of water if I haven't had any rain. From then on, I try to keep my bananas well supplied with moisture. When things get dry, the trees grow very slowly or even stop growing. Their fruit production goes way down. Bananas prefer good soil moisture. They are a good place to divert greywater to, driveway runoff, waste water, etc. My greywater and wash machine discharge never appear to be detrimental to the bananas. The clumps that get this water grow and produce far better than the clumps that don't.
An experiment I did was planting bananas atop a hugelpit filled with old tree trunks & branches, brush trimmings, cardboard, coarse weeds, and layers of chipped up organic waste. The pit soaks up and retains an amazing amount of water from the driveway run off. As a result, the bananas thrive there, are amazingly productive, and never require irrigation even during a drought year. That hugelpit has been maintaining the bananas for several years so far, although I do add more organic material as needed to maintain the surface level. I'm so impressed with the results that I now plant my bananas on fill areas like that, reserving the open soil areas for other fruit trees.