So I have a cucumber magnolia in my yard. It has done well for the last ten years I have lived here but all of a sudden I realized
the entire tree is brown and dead. But there are some new green sprouting off the trunk. Is it dead? Or can I trim it, and if so where do I trim? All the branches have dead leaves. Only the trunk has green.
This tree is relatively free of disease and pests, though Scale pests have been known to attack.
Your yard seems quite shady and this tree thrives best in full sun but will tolerate partial shade, 4-6 hours of sunlight.
The link below is an overview of the care needed.
Sudden death of a tree sometimes can't be explained. It's doubtful the small green still growing from the truck would sustain this size tree.
I would look for a replacement.