Hickory burns long and hot, and leaves a really good bed of coals. Great for heating the house. Not quite as good as hedge, but about the same as black locust. Only drawback to hickory is that it's not very rot resistant so it doesn't last very long on the ground or in the wood pile like the other two. If you load up the stove/furnace with hickory, throw in a piece or two of ash, red oak, or even that walnut. Otherwise it may leave a HUGE bed of coals that needs to burn down more before you can add anything.