There are two items that are using the Poisonous Potato picture.

The first is the normal Poisonous Potato. The second is labeled Regular Potato and is written in italics.

I got the Poisonous Potato from my potato garden. I think I got the Regular Potato from a treasure chest. If not it was from a zombie.

I only have one of each, so I haven't used them yet to see what happens. But I can if you need me to.