skeletal weeper
I understand that using this verbiage contributes to the ghostly setting. However, since “weeper“ is not a common nickname for a weeping willow (google weeper), perhaps the first time it was used, Sonya could have named it a weeper herself. Maybe it could have been something that her grandmother called a weeping willow at her old home. That way, she would’ve introduced this word, and it would have made more sense. I agree that the description of a weeping willow without leaves being called a “skeletal weeper“ is very fitting for this book. However, I think the introduction of the terminology could’ve been written better.