All saplings on the server when grown with bonemeal explode into massive spruce trees that clip through blocks as if they didn't exist, providing nothing of the block you wish to be farming. Only Spruce. All is Spruce. All hail Spruce.
This has caused me a great deal of pain as a human player who can only use Oak for their slime fun buildings. While the shop command is a way of gathering all the Oak one needs it's also very expensive to do in mass quantities especially at the start of the game, not to mention makes the entirety of the sawmill mechanic useless as to buy the Oak Log from the shop to sawmill into extra planks only nets you a $20 profit per cycle effectively taking a viable strategy for early game human currency generation and nerfing it too well below the effectiveness of any of the less fun more currency rich strategies for gaining currency.
As land has already been generated with these custom trees on it providing plenty of nice places to go and look at I suggest the removal of the custom tree plugin so as to prevent further issues with farming. While it is a viable criticism to say that the removal of the mod would make it difficult to have these custom trees on your land the mod does in fact gimp itself via disallowing the production of any trees other than the massive (and quite frankly unsightly) Spruce trees meaning that to get any other more thematically appropriate trees for your build you would have to make them by hand, placed block for block, anyhow and would have to spend exponentially more money to do so than if one could simply farm for the wood themselves.