A tree well is a hole or depression that forms around the base of a coniferous (pine) tree. The holes are formed when low branches stop the snow from compacting and settling around the trunk. The hole is hidden from view by the other branches on the tree. There is no easy way to identify if a particular tree has a dangerous tree well by sight, due to the fact that the low lying branches block sight of the hole. Therefore, treat any tree you cannot see the base of as a potentially dangerous tree well situation.