Okay, I tried growing a subterranean rubber tree, seeing as I spawned in a Dessert with Infinite Biomes on. (Needless to say, that's never a good thing for starting out with). The sapling stayed in its dirt patch through three of a normal tree's growth cycles. I was wondering if this is deliberate or if it's an unintended consequence, or if it's not coded for subterranean growth yet... Or if my area wasn't big enough (5 x 5 x 10). I know it's well-lit, 4 torches, one per wall.
Thanks in advance.
PS I'm guessing treetaps don't work on player-placed logs? O.o