Question
I LIVE IN NORTHEAST PA. AND HAVE ARBORVITAES THAT ARE ABOUT 15 YEARS OLD AND STAND ABOUT 25 TO 30 FT. TALL.      I WOULD LIKE TO TOP THEM DOWN A BIT.HOW FAR DOWN CAN THEY BE CUT,I WOULD LIKE TO TOP THEM AT ABOUT 12- 14 FT. WOULD THIS KILL THEM? THANX ,RON

Answer
Ron,
I would not advocate reducing the Arborvitae's height by half all at once. This would only stress them out and could eventually kill them.
I would recommend that you reduce the heights by 3-5 feet a year, this will allow a period of adjustment for the plants. Keep in mind though, that with reducing the height, the middle of the arbs will be bare and scraggly looking for a few years until they begin to grow up again.
Good luck.
Ed Gulliksen