I've never heard of "clean straw" -- not to contradict, but, where would one get it?
Meanwhile, the regular old straw I use, wheatstraw, does have seeds and so it does sprout, however, it's very easy to pull those out and lay them down creating more organic mulch.... and mostly it gets shaded out or covered over anyway by growing plants as the season goes on. I don't mind a little wheat sprouting.
