In regard to the cow plant, I agree completely with oshizu's post. I've experienced the same thing, including being able to put it into a 2x2 box after it's grown. As for the alien fang plant, my experience was a little different. I was able to germinate it in a pot, but I had to put the pot in a nice open space (I think I used a 3x3 or so, but it's been a while, so it might have been bigger). After it germinated, I was able to move the pot to a smaller area.