Saxicolous. It's not a word that exactly rolls off the tongue, but it's a useful designation for botanists. The word is from Latin, naturally. "Saxum" is Latin for rock, and "colous" (meaning "living or growing in or on") traces back to Latin -cola meaning "inhabitant." Other "colous" offspring include "arenicolous" ("living, burrowing, or growing in sand"), "cavernicolous" ("inhabiting caves"), and "nidicolous" ("living in a nest" or "sharing the nest of another kind of animal"). All of these words were coined in the late 19th and early 20th centuries to describe the flora and fauna of our world.
Word History
Etymology
Latin saxum rock (akin to Latin secare to cut) + English -colous — more at saw