I used to have a nice little bromeliad crypthanthus earthstar bed on my balcony. I covered the pots and surrounding areas with larva stones and it looked quite nice,..for a few months before ferns appeared not only in the pots but also growing amongst the stones. I had to take out all the earthstars and pull up all the ferns.
The ferns I pulled up then were put into a container.
The remaining ferns had to be thrown although it broke my heart to do so. Sometimes you have to be cruel to be kind (to my other plants). Now I need to find my cacti amongst all the ferns in my cacti bed!!!!