No, Fern tea isn't poison, but it doesn't cure the winter blues. Yeah, there is a Indian cure, but it doesn't mesh very well in today's world.
Spring, Summer & Fall were for gathering food and supplies to last the winter. In the winter, when your body and mind slowed down, people did what came naturally and semi-hibernated.
Probably the same thing with your ancestors, right? Running around, trying to work and rush around during the winter is probably working against our natural body rythems.
