Your summer weather goes along way to explain the tree's current appearance. As new to JM ownership, you likely did not supply sufficient water to combat both transplant shock from planting late in the season as well dealing with hot and dry growing conditions.. Without knowing your specific site conditions, it's impossible to say how often to water but you want to ensure the soil surrounding the rootball is kept consistently moist (not wet) throughout the growing season. You can check by digging a small hole next to the rootball to at least the same depth. Generally a slow, long dribble of the hose at the rootball will achieve the best results but a soaker hose will work equally as well. Until you get used to your soil and successfully meeting the plant needs, it is important to check manually.

Home Depot is not what I would classify as a reputable vendor nor do they necessarily purchase from one. To be able to offer the prices the do, they tend to access grower "seconds" or discounted plants. The fact that this tree has no obvious graft indicates it is probably seed grown. Seed grown JM's cannot technically be named cultivars, so your Emperor 1 is really just a species tree. Species or seed grown JM's can be highly variable in appearance, including producing portions that differ visually in leaf size, shape or color,