John Paul Sanborn said:If you burn for heat, then it's a big deal. If it's for ambiance then anything dry is good.
That is if it smells OK.
+1. I'm an ambiance burner, for the time being anyway, and though I appreciate the fire I get off of good oak, walnut, maple, and ash, the faster burning stuff is nice to have for those last few logs of the evening so the fire burns down nicely by bedtime.
That said, willow and cottonwood don't hold much interest for me. The pines are OK, in small quantity, to mix in for fire quality maintenance and fast starting.
If I was burning for heat, then I'd be much more selective.