Who can even grow hay that could be “certified weed free” and afford the cost to continually weed or spray chemicals for weeds? What risk would it be to the grower if a few weeds were found? Crazy world we live in that is being designed to destroy us on many, many levels.
My wife is a certified seed inspector. She inspects fields of wheat and barley as well as grass and Canola so they can be certified as being weed free. Yes they do spray the fields for weeds but this year the wind was so bad that new seeds blew into the fields and they were a mess. If she finds weeds mixed in then the farmer has to “rouge” the field or have crews go through and pick the weeds out.
There is weed-free hay that is free of invasives, or, many packers used condensed hay pellets or cubes, that is cooked enough to be seed-free, and is easier and tidier to pack in.