personally i use the fireplace icon for OAK trees (im building an oak forest ) and boats/rafts etc.. then u can filter them all..

FYI i use the large T symbol as a Menhir locator shipwreck and all stone circles ,the house icon for ANY structure and name it L1 if i build a bed... small circles are b1 =1 blueberry, R1,C1 M1 ... BC is burial chamber with a red X its been explored etc etc piece of cake