Magnolia trees are one of the easiest trees to care for. In fact, according to the Magnolia Society International, once they are properly established, they require minimal care. Magnolias are sometimes susceptible to leaf spots, scabs and blights, but rarely does it ever cause a problem. However, like most trees, magnolias need some care in order to thrive to their fullest potential.
Mulch around the base of the magnolia tree. This will help maintain water and soil temperatures.
Consider allowing the lower limbs to grow and droop to the ground, especially with a Southern Magnolia. This will hide fallen leaves which can freely decompose for extra nutrients. On the other hand, you can prune off the lowest limbs, so you can mow beneath the tree, if desired.
Prune after flowering, if necessary. If you plan to shape your tree a certain way, then do so when it is young (still after flowering) since older magnolias do not heal as well after pruning.
Cut off any roots that begin to circle the trunk.
Water only if you are experiencing a drought. Otherwise, you should not need to water your tree. Fertilizer is not needed.