Forgot to mention, that thing is only about 3 weeks old. It just had tiny nubs poking out of the top that had closed leaves on it. Stuck the other end in the jar and added plain water and poof. This one in particular is actually a Japanese sweet potato with purple skin and white flesh. Regular old sweet potatoes work just fine too.
I had done this once before at another apartment using a normal one, and it took over my entire windowsill. And that one wasn't even getting fed hydro nutes like this one