Kostas

Yes, it’s for good drainage/aeration mainly, plus it binds up nutrients and releases them slowly.

I generally like medium depth, wide holes so that the banana doesn’t get too deep in the clay soil, but rather above the clay soil for better drainage. The roots dig into the clay and enjoy the moisture though but for the corm to be in the clay during a cold winter is not good.
Dig it the way you like the clump to spread eventually as it grows. And take into amount the clump will be more than 1m wide pretty soon

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