Consider finding a "grubber". It grabs the trunk of whatever and if you hook it to the lip of your loader bucket it'll lift out the whole plant. This works really quickly if you have someone on the ground moving it from tree to tree while you move the tractor.
Another way to grub is to set up a triangle of angle iron with a skidding chain draped over a notch in the top. One end goes to the grubber and the other to whatever you're pulling with. Properly rigged it can leverage the pull forces and you don't need to get near so can be done in tight surroundings.