Something I've learned about through my autodidact pursuit about learning about trees is what chaga is. Here is a photo of young chaga on a birch tree in my Connecticut woods. I took the photo in December 2007 but didn't know what it was until a few months ago. I was curious about it back then but never took the time to figure it out until this year. Chaga has medicinal properties and has been used by people around the world for thousands of years. I have not yet wildcrafted chaga myself or used store bought chaga.