[2020] Why this? Surely mod conflict...

If you use Prop and Tree Anarchy, your best option is to just remove any props and trees you won't want. If you set it to hide everything on load, then areas you have decorated using the mod (so where you want trees not hidden) will also disppear. The game and the mod can't tell which trees/props we want to see, and which ones we don't want. So remove the ones you don't want or remove the mod.

In addition all the hidden props/trees are still there. You might not see them, but the game still knows they're there and which ones they are. This means they are still taxing your system. It's a waste really. I recommend deleting them - even if you end up not using Prop and Tree Anarchy, you're still better of removing things than having the game hide them.