Bill wrote:
After 35 years I have two large Magnolias about 30 feet high. I
intend to take one down for more light as it blooms too early an burns
due to frost. The other is close and one branch could rub against our
roof. The latter concerns my prune question.

Can I trim it back ?

Been here.

http://www.rhs.org.uk/advice/profiles0603/magnolia_prune.asp

Bill

I've got one and I'm constantly whacking away at it. Not pruning to
shape but removing lower branches and those that threaten house.
Wish my wife never brought it. It's beautiful right now but drops
blooms fast and they need to be raked as they smoother grass and clog
mower. Leaves in fall are also a PITA.

http://home.comcast.net/~frank.logullo/magnolia.jpg


Frank