Experts and BHG readers answer.
About a magnolia tree.
Digging a plant in midsummer and moving it is always risky. No matter how careful you are to get as many of the roots as possible, you'll be cutting off up to 90% of the roots. It will take a some time for the plant to regenerate nw roots before it puts out new top growth. In the meantime, keep the root system moist (but not soaking wet.) Avoid fertilizing the plant until it becomes re-established.