Hmm -- put in that the trees were deliberately frozen like that by weather magic. And the characters have reason to believe that it will not be used on them.
-- which does not fix the problem because the whole reason I first put that neat notion in is that it sometimes happens in real life. Without visible magic in play.
Hmmm -- it won't happen naturally. And we can have one of them wonder about it, and the other fill her in the reasons why, revolving about the magical winter they face. Since they were carefully orchestrated so that one of them is ignorant, and the other knowledgeable, about everything I need info-dumped.