Hi, 

From these photos we are unable to diagnose the cause of the decline. We would recommend you contact a certified arborist or licensed tree expert to asses the tree in person. 

Sweet gum trees prefer to have a little more water than to be on the drier side. Have you watered the tree in times of drought? Last growing season was very dry and we are seeing well established and mature plants suffer from the lasting effects of drought stress. It may not have been the sole factor in decline but multiple stress symptoms compiled unto the tree could have. 

We can't see the root flare and bottom part of the tree due to the plants at the base. Is the root flare buried by being planted too deeply or mulched too high? These are common planting mistakes that can be detrimental to tree health. Often times trees that we plant from the garden center or nursery grower come buried too deeply in the container or burlap from when they dug the tree in the field and homeowners and landscaping crews are not aware of that at planting time, burying the trunk of the tree and causing girdling roots, disease or insect problems and nutrient exchange issues.

Also not the sole cause of decline either, but english ivy growing at the base and up tree trunks can be problematic for tree health down the road. English Ivy is considered an invasive plant in Maryland so we would recommend removing it. It can harbor disease and heavy vines can weigh down the tree causing limbs to break and dense foliage can block the sun from the leaves. It also cause wood rot from being against the trunk.

We also noticed that the tree is planted very closely to the utility boxes. If the companies have done work in the last few years and disturbed the root zone, it could have taken a few seasons to cause the die back in branches. 

You can refer back to us when you hear from the tree experts and we can consult on their advice. 

Emily