Himalayan blackberry (Rubus discolor) is a shrubby weed that is native to Eurasia and has naturalized throughout California in riparian areas and other moist, disturbed sites. This plant forms dense thickets that become a thorn in the side of Mother Nature and land manager alike. Himalayan blackberry is known to take over entire stream channels and ditch banks shading out nearly all other vegetation.
In California, Himalayan blackberry is the most common blackberry picked and eaten by humans. The stems are covered with heavy, broad-based prickles and the larger stems are distinctly five-angled. The leaves are clustered in fives and their undersides are white. The white-to-pinkish petals are each about 10-15 millimeters (0.4-0.6 inches) long.
There are several species of native blackberries that could easily be confused with Himalayan blackberry. In the foothills, California blackberry (Rubus ursinus) often grows alongside Himalayan blackberry. California blackberry is distinguished from Himalayan blackberry by having the leaves clustered in threes rather than in fives (usually). The stem of California blackberry is round, not five angled as in Himalayan blackberry. The underside of California blackberry leaves are green, not white like Himalayan blackberry leaves. The prickles on the stems of California blackberry are narrow and straight while Himalayan blackberry has curved prickles with wide bases.
At higher elevations there are two other blackberry species that could be confused with Himalayan blackberry: blackcap raspberry (Rubus leucodermis) and smoothleaf raspberry (Rubus glaucifolius). Both blackcap raspberry and smoothleaf raspberry have leaves clustered in threes (usually) and round stems. There are several other blackberry species in Sequoia and Kings Canyon National Parks, most of which are native. These species have smaller, less palatable berries. More importantly, their leaves are generally clustered in threes and their stems are smaller and more rounded than the angled stems of Himalayan blackberry.
NPS photo by Athena Demetry
Himalayan blackberry is capable of reproducing both vegetatively and by seed. After reaching a certain height, the stem tips will bend down to the ground and root. The plant also sends out adventitious rootstocks (suckers), enabling it to spread slowly from its source. Birds are capable of distributing blackberry seeds to great distances. There are even reports that passage through a bird's digestive system could increase seed viability.
There are several large infestations of Himalayan blackberry in Sequoia National Park. The most extensive recorded population is in Yucca Creek, a tributary of the North Fork of the Kaweah River. There are also small populations in the Middle, East and South Forks of the Kaweah River. Himalayan blackberry is considered a very difficult species to control because it is so successful at vegetative reproduction and because it often grows in very sensitive wetland habitats.
Two removal methods are being used on Himalayan blackberry. The first method consists of cutting the canes and then grubbing the roots. Resprouting is generally abundant, and many years of follow-up are necessary. The second method involves hand cutting of canes followed by a highly targeted, cut-stump application of approved herbicide (glyphosate) in the fall, when carbohydrates are being translocated to the roots. Foliar applications of glyphosate have also been used. This method is necessary on rocky stream banks where hand removal of roots is not possible. In 2002 park resource management personnel began the process of eradicating this plant from the parks. Efforts were focused on the Yucca Creek populations.