Definitely use the old hay that's been sitting out in the weather. The fresh hay (definitely if it's 1st cutting) will likely have viable grass/weed seeds in it. The moldy old stuff won't. Also be sure that the hay doesn't contain any broad-leaf herbicides - again, the older stuff is probably safer in that respect (though some herbicides are persistent, essentially the inside of the bales have been "cooking" and I think 2-3 yrs is safe even if the field had been sprayed). But best to take a tomato plant, if you have one to sacrifice, and muclh it with that hay now, see if it starts shriveling. You can cover your bare earth with burlap or plastic while you're waiting for the test results.

we used straw many years ago when it was cheap, mostly it comes from the wheat harvest so does have left over seed in it (they haven't made a harvester yet that can harvest 99%of the grain), anyhow yes we did get some sprouting but it hardly qualified to be called weeds! we simply pulled them where we could and tucked them under the mulch as extra nutrient. but there was never any perpetuation of the growths even if they did reach some sort of maturity. we use hay type mulches now more affordable and contain better nutrient values, these can contain seeds (in the case of pasture grass that is baled for fodder purposes) but there we hardly ever get any growths, and again they hardly qualify as weeds. we mulch to around 6" to 8"s and this probably also helps in control of any seeds that may germinate, plus we remulch about every 6 monhts as a minimum. len Here is a link that might be useful: lens garden page

Using it as mulch, right, rather than in a compost pile? On top the soil around the plants but not right up next to the plant stems? Yeah, if your soil is now warm enough to layer on mulch, it will be good stuff. Hay and straw are some of the best mulches there is. How much composting in place it will do and how much nutrients it may or may not provide will all depend on how "old" it is and what the mix balance is. But by fall you can till it in with no problems. Dave

lavender_lass: Your plan for using spoiled hay should work as long as you patrol for slugs & water weekly if no rain. I've used it numerous times & despite warnings about seeds sprouting I've not had much trouble with either. Straw seems to last longer, but both work. Depending on how much hay you have you might need some layers of cardboard or thick newspaper to stop the onslaught of the weeds/grass. What sprouts in the hay isn't going to be much of a problem even if only tended once a week. Either stack more hay on the sprouts or give a quick tug or hoe action & you're done. I usually run out of hay before my project is complete, so having a huge supply is a bonus! I gather the free sweepings from the feed store, so usually a mixture of straw, alfalfa & grass hay. A big bonus of this method is that next year you'll have an an easy to plant bed with fluffy soil under that hay. I found that out by accident and now know it's called sheet composting. Sure saves me time & energy from having to weed the garden. When our kids were younger they'd ask why the other gardens they'd see had 2' high weeds & my reply would be, "Needs mulch!" I wouldn't garden without it anymore. Some basic tips that have helped us with these crops. potatoes-- leave at least 2-4" green showing to keep them growing. Some varieties will produce a larger harvest with more mulch being added, but Yukon Golds don't. Still the hay mulch keeps it moist so you water less & potatoes continuously grow. pumpkins-- put a board, brick, flat rock, or even right side up Frisbee under the pumpkins to keep them drier & away from the slugs who love to hide underneath. Anything that doesn't collect water or stay damp should work. After harvest, be sure to chop up remains with a hoe or mower, then smother with more hay so you have at least a 6" layer that will be a snap to plant in the spring. Corrine