Sometimes when people do not know or think it is "too hard," they plant vanilla trees. It is annoying. I would like to see a feature that allows custom trees to be grown from saplings, if this is not an extreme request.
Another plugin suggestion: I just created a small plugin that will replace the normal, tiny vanilla trees with the improved(large) version. It was not made for Loka, but it would not interfere with any existing plugins and it would make the sapling-grown trees that people place because they are a bit too lazy to create their own custom trees less annoying. https://www.dropbox.com/s/qwwd3rlgkhylmfe/BetterTrees.jar?dl=0