I prefer star magnolias as a shrub, but of course that is my own preference. We have a lot of rain and autumn/fall gales here and those that are grown tree "like" can get top heavy if not looked after and do tend to get damaged at this time of year! Over here they can get mildew and other diseases as it is damp so I like to get air into the centers of them, so thin them out quite a bit. I do prune mine and my mothers quite vigorously and to two nodes to make for more condensed flowers. I try to keep mine as compact shrubs and not too leggy as they can and I have seen it happen, snap quite easily in a gale.
I was taught to always walk away from them and then look at them from different positions and you can see what needs to be pruned out. This works with some pruning, but not all pruning takes to this.
Sometimes they are best left well alone if you have the space and protection from the winds here.
Regards.
Neil.
