I suggest naming the trees or descibing the trees as cuttable somehow. Like "You see old sick tree; there won't by any use of it." and something diferent for the trees that are strong and we can cut them for wood.
The trees in ncr near the inner wall are choppable, look for the ones with roundish tops.
Look at the worldmap for hilly areas, and look there. Nearly every map with a cave on it has also choppable trees there.