File this in your "someone in Iowa has too much time on their hands" folder. According to the Iowa Tax e-News, issued by the IA DOR, as quoted in the CCH's State Tax Review, of October 12, 2007, only certain kinds of pumpkins can be purchased tax exempt in IA.
This type of thing is always great news for grocery stores. Get this: Pumpkins are only exempt if: (1) the buyer completes a sales tax exemption certificate stating they will be using the pumkin as food. Oh, my, so stores will have to maintain copies of these certificates too.
But wait! There's more. The store can't just take the certificate and go on, they have to verify that the particular pumpkin purchased is a specific variety that would normally be used for pumpkin pies.
There is one safe-harbor though. If the pumpkins are purchased with food stamps they are exempt.