Planting Star Magnolias

Q: In late July, my star magnolia, planted last fall, suddenly almost completely defoliated. I kept it watered through the winter and only occasionally this summer since rain was frequent. It looked healthy in early July. Any idea what the cause is?

A: It sure sounds like a water or root issue to me. I know you watered this summer but my bet is that the roots have not lengthened very much from the initial planting. Slow root expansion is particularly common when roots in the original root ball are not untangled before planting. I know the planting tag for many trees and shrubs indicates that digging a hole a couple of times wider than the root ball is sufficient. But new research shows that removing most of the potting soil and untangling the roots to spread them in all directions in their new soil home is the best planting method. Grasp the trunk of your tree and try to wiggle it back-and-forth. If the root ball moves very much, the roots have not grown outward as much as needed to survive a short dry spell.