[R. penetrans L. H. Bailey]
This thorny scrambler is a noxious weed which rapidly invades disturbed areas between 1,000-2,300 m. It forms impenetrable thickets which expand by the rooting of aerial shoots where they bend over and touch the ground. Alien frugivorous birds are the principal dispersal agents. The aerial portions of a plant are normally destroyed by fire but the plant quickly recovers from basal and subterranean shoots. Several biological control agents have been introduced but they are not very effective. Two rust diseases are currently under investigation by the National Park Service (NPS) and U.S. Forest Service (USFS). Some biocontrol agents introduced to control this species have affected the 2 native Rubus species.
The species is well-established in mesic to wet forests between 600-1,700 m on all major islands.