I'd say they are hardy. They're growing on a piece of lr the size of a baseball that was dry rock. Sat for a month at my house for a month after buying before i even tossed it in my tank. Then a month later boom. First little head. That was almost a year ago. I only have a half a dozen heads now. But little babies ready to pop soon. I see sites selling them for 15-25 bucks a polyp. That seems a little excessive. Crazy. Much appreciated rob. Guess i'll have to be patient ontl those purple ones until i can stumble on them.