bencelest

Baby it like a baby. First get anything to cover it like a too large black pot so it will not touch the leaves. The last thing you want is the sun to shine on it. Remove the cover once the sun goes down. Do this for 5 days or so until you see that the leaves stay turgid. That means the roots are starting to grow. Then gradually, increase the exposure to sun 2 hrs more at a time. Don't over water. As long as the soil is moist that's all you want.
When it can fully stand the full sun, wait again until you see some spears started to appear that's when you start to fertilize. Again 1/4 dose the first time and see how the plant takes it then increase the dosage. I repeat do not add any fertilizer to the soil when you plant your banana except as many compost as you can and bark. I'd say in 2 months you will have a nice new plant and nice growth.
Also remove the brown leaf. You are not too late to do the above.

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Banana Nut