The teapot Sonja got a handle made out of birch roots with a core of electroplated nickel silver. I dig up the roots in my family’s forest during summer, peel them, split them in the middle, soak them in warm water and then wreath around the silver. This is an old craft which was used all over Sweden once but it has its strongest connection to the sami culture in the north.
The same technique is used all over the world but with different materials depending on where you are. A common material is grass
There can be some roots of spruce in the handle as well. When I dig up the roots it is difficult to differ between the species and the forest has a wide mix of different trees. However, spruce roots fits perfectly for binding too.