frost on trees; hoarfrost on trees
General term for ice crystals formed on trees by freezing fog or moisture. Often used in meteorological contexts.
snow monsters; frost-covered trees
Refers specifically to the dramatic, large-scale frost formations on trees in certain regions like Zao, where they are called 'snow monsters'. More of a tourism and local term.
It was so cold this morning that frost had formed on the trees in the mountains.
The frost-covered trees of Zao are famous as 'snow monsters'.