I like digging and building large underground bases. My current one goes to bedrock (-58 'y' coordinate) and I have found the large spruce trees will not grow at a negative 'y' coordinate. The small ones will, but the large ones will not.
Tested with 16 blocks clear above saplings with no blocks being within 2 blocks of saplings at a negative 'y' coordinate.
Tested with 32+ blocks under same conditions
Tested with 32+ blocks under same conditions with the sky showing as well.
In the end, I could not get a large spruce tree to grow until I went to a positive 'y' value.
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We're tracking this issue in MCPE-126254, so this ticket is being resolved and linked as a duplicate.
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