My neighbors have huge burning bushes (about 12' tall) planted about 3' away from my chain link fence. Although the bushes are beautiful, they have become a nuisance -- extending at least six feet into my yard, making it difficult to mow and maintain the fence line. I plan to ask the new owners of the house if I can trim them back. What time of year should I do this? How far back can I prune without damaging the bushes? Thank you.