Hey there,
Look in to some discussion on planting basjoo deep. I grow them here in WV, where our winters are horrible. Most of mine are planted up to 2 feet deep. Though I didn't protect any last winter, I have before and continued the growth the next season by up to three feet to start with. Even without protection, one of mine is already putting leaves on the roof of my garage.

Even though they have started from near ground level is year, the leaf size just about picks up where it leaves off in the fall

I do however, always keep at least two inside as insurance, but since I work in a school, I have lots of sunny places to put them.

I do have one at ground level that has lived,but there is always a piece of the clump which rots out each year. The only time it didn't, it was protected by garbage bags of leaves and wood shavings piled on top of it.

I just use plain old miracle grow, but I need to look in to the milogranite.
Good luck,
Chris

My personal opinion based only on 5-6 years of growing and observation is soil preparation. From north central Alabama to the gulf coast I've seen bananas planted in the local soil from clay to sandy soil with little or no amendment & they are small in height. I believe
the corm needs room to grow and expand with ease to get the growth on the P- stem. My nanners are 12-15 ft. tall & my younger plants not far behind and catching up.When planting, I dig out my local clay soil and discard. Dig a large hole and fill with store bought pine mulch and so called top soil (bagged). The cheap stuff. Not the high dollar potting soil. Make it wide,deep ,loose, and organic. I will also rake up and add any natural mulch in the area,leaves,etc.Water and fert &I they will grow like crazy. I add new pine mulch in spring and fall. Just my opinion; #1 is soil #2&3 is water and fertilizer.

My personal opinion based only on 5-6 years of growing and observation is soil preparation. From north central Alabama to the gulf coast I've seen bananas planted in the local soil from clay to sandy soil with little or no amendment & they are small in height. I believe
the corm needs room to grow and expand with ease to get the growth on the P- stem. My nanners are 12-15 ft. tall & my younger plants not far behind and catching up.When planting, I dig out my local clay soil and discard. Dig a large hole and fill with store bought pine mulch and so called top soil (bagged). The cheap stuff. Not the high dollar potting soil. Make it wide,deep ,loose, and organic. I will also rake up and add any natural mulch in the area,leaves,etc.Water and fert &I they will grow like crazy. I add new pine mulch in spring and fall. Just my opinion; #1 is soil #2&3 is water and fertilizer.