I don't your particular cultivar, but my SM didn't do much the first year I transplanted. Very little growth all season and then some cold damage the following winter had me sweating bullets. This year, it was off to the races and it has already grown 1.5 feet in height since March! The earlier poster had it right I think they don't handle transplanting well. Hopefully, if it was rootbound you unwound that taproot at the bottom. Also remember that certain soil types (like clay) which magnolias tend to like also have a tendency to retain water. MT

March 9, 2009 - Update I checked all magnolias - all except for Edith Bogue have burn on their leaves. The burn is not severe, however the winter has been colder and windier than normal. My magnolias normally lose leaves in the spring when new growth begins so I am not too concerned with springtime leaf dropping. The trees have burlap screens on the side where the Sun would normally shine on them in the afternoon and the burlap is on the side that the winds normally come from. I gently "wiggled" random buds on all Magnolias. A stiff rigid bud indicates winter kill and possible die back. All buds that I tested were flexible indicating that they survived to this point. I have done this last year so I am confident that they have survived the worst of this winter.

it does not need to be re-wrapped ... the leaves probably died when it was transplanted in the wrong season .. and in the wrong heat wave [there is not a good heatwave] ... i am surprised it has lived at all ... so you must be doing something right.. we can not tell you how water moves in your soil.. only you can insert your finger.. or dig a small hole [outside the rootball] and insure there is water in the root zone ... in mid to late august.. i would not really be concerned with some spots ... EVERYTHING.. everywhere is stressed and tired after a long season ... do not use chemicals on a stressed plant.. nor organic cures ... for black spot or mildew nor fireblights.. nor anything else ... it doesnt matter what it is.. ignore it ... IMHO do not fertilize... and please tell me the exposed root mass.. which is proper planting in most clay ... is fully and properly mulched.. and not exposed to blistering sun ... listen to me carefully ... you are on the right track if you planted a 9 foot tree in late june in TX.. and the thing is still alive ... do NOT now... try to kill it with too much TLC .... you must insure the watering is proper for the rest of this year.. and all winter.. and for the next 2 years ....... pix might change my mind .. continued luck ...you seem to be on the right track ken

I don't believe that the leaves have allelopathic properties, but wood chips from magnolia have proved to inhibit the germination of certain seeds.