Burning Buckthorn in Winter

This video shows how I attempted to get rid of some buckthorn in the winter by burning it. Very slow process, and barely made any damage. One way to do it, but not a very effective way.
This is a very remote part, and I cannot bring any machinery up there such as a bobcat, brush remover, etc.
In my area, you do not need a burning permit if there is snow on the ground.