Weeping cherry die back
The split in the trunk of your weeping cherry is from sunscald/winter injury. Thin-barked trees such as cherry are susceptible to damage in winter when the sun is at a low angle in the sky. The trunk heats up during the day, and at night when it cools off quickly, ice crystals form in the trunk, killing some of the cells. The damage may not be evident for a couple of years when the rest of the trunk grows and expands, but the dead portion doesn't. This causes the bark to split at the dead section. Because nearly the entire top portion of your tree is affected, it may die back completely to the damaged area. It's possible that the tree may send out new growth below the damaged section, but because weeping cherries are grafted on top of an upright stem, the shoots that develop below the damage will not be weeping cherry.
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