For Christmas my husband is having a hoop house built for me. However the plans call for treated lumber to be used around the base. What can I use instead. Would cedar work and how expensive is cedar?

Cedar will be around LONG after you and I are gone! Be prepared to pay the price, though. Unless you know someone with a tree service, it is pretty pricey. I have heard the farmers used to use post oak for fence posts, but I doubt you can find it milled. I suppose any other oak might work, but it is somewhat expensive too. I don't know for sure, treated lumber is pretty expensive as well. I would just shop around. Good luck.