Himalayan Blackberry
Rose Family
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.
Identification
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.
Look-Alikes
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.
Natural History
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Mature stems of Himalayan blackberry are
squarish and angular with heavy recurved prickles. Note that the
leaves are clustered in fives (and sometimes in threes).
© NPS photo by Athena Demetry.
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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.
Management
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 and East
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. 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.
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