5 Trees with Medicinal Bark for the Winter. First, what is a “medicinal tree?” When I use that term, I specifically mean a tree that I was able to find multiple historical sources documenting their herbal applications. I picked the trees for this video because they are common and have traditional uses for typical conditions in the wintertime. Additionally, you’ll notice that the bark is the medicinal component of each of them. That means you can find and gather them even in the middle of winter!