Replace grass with ferns in lush caves

I like the new lush caves, but I'm not a fan of ordinary grass spawning inside of them.  Grass is already so common on the surface.  Real life lush caves have ferns and mosses, not grasses, which are full sun plants that thrive in dry, sunny areas.  Lush caves should have low light and high moisture plants like ferns, maybe even club mosses and liverworts (weird, blobby looking things).  The ferns could be the same as surface ferns, just with a warmer shade of green than the ones in taiga biomes.