Hay vs Straw
Lateley I have been seeing several posts comparing Hay to Straw and some confusion between the two.
There may be some regional differences in quality etc.
My responses are what I see in Wisconsin
Hay - Results from cutting green grass, clover etc. and the resulting bales are typically meant for feed.
Most hay is alfalfa which should be weed free. Typically the higher the quality the less weeds. "Dairy quality hay" would typically have the least amount of weeds if any. This is normally cut just prior to or the very beginning of blossom of the alfalfa. The fields are ripped up if too many weeds start growing since it will dramatically affect the feed value of the hay.
A lot of "horse hay" has a mixture of different types of grasses, clover, possibly alfalfa etc. Quite often this is cut when the plants have already headed out.
I have also seen people cut abandoned pastures, waterways, ditches etc, bale it up and call it hay. The feed value is marginal with a lot of chance for weeds.
Some farmers may use oats as a cover crop when seeding alfalfa. They have a choice to let the oats mature, combine, bale as straw or cut it when it is still green before it heads out and bale it as oat hay.
Straw is the hollow stalks of wheat, oats, barley, rye etc. from after they are combined.There is relatively no feed value in this. Again, this should also be relatively weed free. Along with the stalks, you will see the seed heads of the plants but the seeds should have been removed. The combines never get all of the seeds so you will quite often see volunteer wheat etc growing from these. This all depends on the fields. I have seen some grain fields that had quite a few weeds and needless to say, the straw that comes from those fields will have weed seeds. Straw is typically cheaper than the high quality dairy hay, but similar to some of the lesser quality hays.
Never dealt with pine straw, or salt marsh hay.