Question
Is there a chemical that can be put on arborvitae in order to stop their growth? I would like to keep a group of them at a certain height to avoid them from growing into the utility lines.

Answer
One growth regulator is Atrimec
Trim shrubs to shape, leaving at least two pairs of expanded leaves on each shoot to absorb the spray. Apply within three days. Two treatments per season is usually required. for Arborvitae mix 1 FL.OZ./GAL of Atrimec and spray the entire plant.
Check with your local nursery for atrimec.