OISC target species
Himalayan blackberry

Himalayan blackberry

Rubus discolor (Rosaceae)

Himalayan blackberry (Rubus discolor) poses a threat to natural areas in Hawaii by forming dense, impenetrable thickets that exclude other native plant species. Such thickets also make access difficult for hunters, hikers, and other visitors to forests. Although Rubus discolor is not on the list of plant species designated as noxious weeds  by the Hawaii Department of Agriculture, several other Rubus species are on the list. The Division of Forestry and Wildlife of the Hawaii Department of Land and Natural Resources has designated all species of Rubus as among Hawaii's Most Invasive Horticultural Plants. Himalayan blackberry, native to Eurasia, is a perennial bramble with sturdy, 5-angled, thorny stems. It overtops native vegetation and forms impenetrable thickets in riparian areas, marshes, and oak woodlands on the West Coast from California to British Columbia. The California Exotic Pest Plant Council considers this species a "most invasive wildland pest plant." Rubus discolor is a high priority for control because it poses a potentially serious threat to natural ecosystems and outdoor recreation, and because it currently has a limited distribution on Oahu. Other Rubus species, such as Rubus argutus (prickly Florida blackberry) and Rubus ellipticus (Himalayan raspberry), have proved to be highly invasive and disruptive to native ecosystems in Hawaii. Prickly Florida blackberry has already destroyed habitat for many important species in the wetter regions of the Waianae mountains and has hindered management of such areas due to its thorny thickets. Currently, Rubus discolor is the only species of blackberry in the Koolau Mountains and is known from only two areas on Oahu: Mauumae Trail and Palolo Valley in the southeastern corner of the island. Other Rubus species are bird-dispersed, and several fruit-eating birds are common in the areas where Himalayan blackberry grows on Oahu. It is likely that the fruit is ingested and dispersed by such bird.

For more information:

• Himalayan blackberry flyer  from the Oahu Invasive Species Committee (OISC)
• Rubus discolorspecies information from Hawaii Ecosystems at Risk (HEAR)