Daisy ...
I think it depends on when and where you take the "nip" and how deep, the cut. My major shaping is after the bloom period, then the "nipping" is after the bush leafs out, and I want to encourage smaller branching to fill in, or not to fill in as I see the leaves develop. By fall, I'll wait until next season to mess with the plant some more, but I never allow any more top growth.
That said, this is the first time I have ever grown a magnolia tree ... so what do I know ?
