potions, plants, holy bowls, arrows are stackable.
If you have potions with different values, they will stack seperately. E.g.: you have the alchemy extract skill on lvl 2 and make a small potion. This will have the values of a medium potion and therefore you will see 2 stacks of small potions in your inventory, but only one icon in your potion bar.
Stackable items will stack themselves, you don't have to do that yourself.
Kiya
