That one trunk appears to have sustained some terrible injury at some point, be it some equipment bumping into it, a lightning strike or even an animal repeatedly visiting it. Either way, the tree is unlikely to successfully seal over that large of a wound.

If it were me, I’d remove that one trunk and the rest of the tree should do okay. It may shock it for a bit, having that much of the leaf canopy removed at once, but it’ll likely bounce back. Keep a close eye on it too for insect infestations. They tend to know how/when to take advantage of a stressed tree.

The lichens and moss growing along the trunk don’t bother me. They’re not parasitic, so they’re not robbing the tree of anything.

Premier Tree Solutions’ certified arborist Rafael Santiago concurs, saying “I see this happening to ornamental cherry trees all the time! Unfortunately, these trees are not great compartmentalizers, so when there’s an injury (either mechanical or biological), they take forever to seal that wound. In the meantime, the open wound is an invitation for more pathogens that makes the compartmentalization even more challenging. But the good news is that I don’t think the tree is dying - though that entire limb needs to go! Cut back to the branch collar at the trunk.”

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