Yeah, I was surprised about the pine. Black walnut, yeah, I can understand that. I read another site that said basically, any wood EXCEPT for aleopathic types, like walnut, and those that don't break down well is acceptable. Oh, yeah, I can see that willow would be a problem. Those things can come back from the dead, it seems.I have had great results in my hügelkultur beds that were filled with pine and spruce logs. I have used both old rotted pine wood and freshly cut pine wood in my beds. My plants have been growing well. Not sure how much better the plants could grow if I had used some other type of wood.