I remember about 15 years ago when I helped a friend finish a cabin in the woods. He used a wood stove to heat it and usually collected ash, mulberry, elm, and cottonwood. I asked him which one of the three he liked best. He thought for awhile and said. "When I want to get the cabin warmed up fast in the morning, I reach for the cottonwood. If I run out of cottonwood, the elm is next. Nothing warms this building up faster, and when I'm cold, I have no patience."