People use the words interchangeably, and every fall a lot of porches end up with the wrong one. The difference matters more than the vocabulary suggests.
What each one is
Straw is what's left after grain is harvested. The seed head is gone and what remains is the dry, hollow stalk — wheat, oats, barley. It has almost no nutritional value, which is precisely why it's cheap and why it's used for bedding rather than feed.
Hay is a crop grown and cut to feed animals. Grasses and legumes, cut green and dried with the leaves and seed heads still attached. It's food.
Look at them side by side and straw is pale gold and uniform, hay is greener and mixed, with visible leaf and seed.
Why the difference shows up on a porch
Hay attracts animals, straw mostly doesn'tHay is feed, and rodents, deer, and birds treat it accordingly. A hay bale on a porch is an invitation; a straw bale is furniture.
Hay carries seed. Straw carries much lessSeed heads mean sprouting, especially once a bale sits through a few weeks of rain. A hay bale that greens up on your steps is doing exactly what it was grown to do.
Straw holds its shape longerHollow stalks bound tightly make a rigid block. Hay is softer, packs denser, and slumps sooner once it takes on water.
Hay holds moisture and molds fasterGreen-cut material with leaf attached retains water in a way hollow stalk doesn't.

What we deliver
Straw, in every package and as an add-on at $30 a bale. There's no version of our display that uses hay.
That's not a preference. Hay would cost us more, attract more animals, and look worse by mid-October, which makes it the wrong choice three separate ways.
If you're buying your own
Ask which it is rather than guessing from the picture. Farm stands and garden centers sell both, often side by side, and the signage isn't always clear.
Pale gold, hollow stalks, no seed heads, and a tight bind is straw. Anything green, leafy, or soft is hay, and it belongs in a barn.
Getting the most out of a straw bale
Set it string side down, so the strings run across the top and the cut stem ends face out to the sides. A bale resting on a cut end wicks ground water straight up into itself while rain works on it from above, and that's what turns a bale soft and moldy. Keep it out of the low spot where water pools, and if it's sitting on soil or grass, raise it on a pallet or a pair of pavers.
A dry, tightly bound bale holds its shape and sheds very little straw. A soaked one slumps, darkens, and comes apart.
At the end of the season
Straw is genuinely useful afterward. Broken up over garden beds it works as winter mulch and breaks down by spring, which is more than you can say for most seasonal décor.
If you'd rather not deal with it, Season Removal takes the bales along with everything else.