A reader writes in and asks, “What’s the difference between hay and straw? Which one should I mulch my garden beds with, or does it matter?”
A: Hay is grass or grain (clover, wheat, barley, alfalfa, timothy, oats or rye) that has been cut to use as animal fodder. A farmer will use a combine to pick grain and feed it to his cows, goats, sheep, horses, etc.
(To avoid confusion on this site, any time we refer to the leftover pile that accumulates after you mow your lawn, we will call those grass clippings).
Straw is the remaining, hollow stems after the grain has been picked and threshed. It is used as an absorbent bedding for barn animals.
(We found this great article on straw and hay.)
If you’re looking for an absorbent, biodegradable material to protect your garden beds with, use straw and not hay. Certain garden vegetables such as strawberries (makes sense, right? STRAWberries?) and potatoes do best when buried in a nice, thick layer of straw.
Hay (cut grass or grain) contains seeds that will germinate in your vegetable garden and cause all sorts of unwanted growth.
Be aware that some farms don’t do a good job of keeping hay seeds out of their topsoil. We purchased some for our garden a few years back and ended up with a few errant corn plants (we did not plant corn and don’t have room for corn), as well as a whole crop of invasive weeds.