Yep, don't use hay unless you know abso-dang-lutely it is seed free, otherwise you are doing more harm than good. The hardest part is finding enough GOOD mulch to use, because to be effective the mulch needs to be at least 2 inches deep or you might as well keep the hoe sharp and at the ready. I would also try to avoid pine bark mulch and get hardwood if you can find it.