Invasive Weed of the Month: Himalayan Blackberry
By Cathy McQueeney
The Himalayan blackberry (Rubus bifrons) tantalizes us with its sweet fruits in the summer and tortures us with its prickly vines all year long. Also known as Armenian blackberry, this wide-spread and aggressive weed is native to Armenia and Northern Iran. It is considered an invasive species in many parts of the world, including Clackamas County.
In Oregon, the Himalayan blackberry is designated as a Class B noxious weed. It is found in much of western Oregon and is not actively surveyed, even though it is a weed of economic importance. Propagation, transport and sale of this plant are prohibited by law.
One can find Himalayan blackberries throughout Clackamas County, thriving on unmanaged sites, disturbed areas and along stream corridors. Due to the spread of seed by birds, it is also commonly found under perching sites, such as along fence rows and under power lines.
How Can I Identify Himalayan Blackberry?
Himalayan blackberry is a tall, semi-woody shrub with thorny stems and edible fruits. It grows upright on open ground and will climb and trail over other vegetation. Mature plants can reach up to 15 feet in height. The canes of Himalayan blackberry can reach lengths of 40 feet and are typically green to deep red in color. Blackberry flowers have five white to pale pink petals. Himalayan blackberry forms dense, nearly impenetrable thickets or brambles. In some instances, canes can reach densities of more than 500 canes per square yard. Canes typically last only three years before dying off, so dense thickets are often dominated by old canes.
Why Should I Care About Himalayan Blackberry?
Removing blackberries from public and private property is an on-going battle. The plant aggressively reproduces by seed which passes undamaged through the digestive tract of many birds and animals. This seed can remain dormant in the soil for several years. The canes of adult blackberry plants will also root where the tips touch the ground. These roots may reach 30 feet in length and extend 2-3 feet deep. Unfortunately, even small root fragments can develop into new plants.
Managing this invasive weed requires the investment of significant resources in time, equipment, labor and herbicides. In the case of agricultural land, infestation by blackberries can reduce the available land area for farming. It can also significantly increase farming costs which are then passed on to consumers in higher food prices.
Habitat for wildlife is also disrupted when blackberries form dense thickets which crowd out many native plants. Many of these native trees and shrubs provide shade and bank stability along rivers and streams. In forest land, older canes can build up a substantial litter layer which may serve as fuel for wildfires.
When Should I Control Himalayan Blackberry?
Autumn is an ideal time to manage blackberries on your property. During the spring and summer months, birds and small mammals often use the thorny brush to build nests to protect their young from predators. Blooms attract pollinators and berries are attractive to people, birds and other animals. Desirable plants that coexist with blackberries are also actively growing during the spring and summer months, so control activities on blackberries during this time can be potentially harmful to them as well.
In the fall months, our native plants have largely died back or become dormant for the season, baby birds have left the nest and the blackberry flowers and fruits are no longer attracting wildlife. At this time, blackberry plants are reallocating their resources down into their roots, making fall the ideal time to manage these plants with a targeted herbicide application. Should you choose to use chemical control, ALWAYS FOLLOW THE LABEL and put safety first, for you and any unintended targets.
If You Like Berries, Plant a Native Instead!
Pacific blackberry (Rubus ursinus), also known as trailing blackberry, wild mountain blackberry or Northwest dewberry is the only blackberry native to Oregon. Its smaller, sweeter berries have fewer seeds and ripen earlier than Himalayan blackberries. Instead of forming huge brambles, these plants trail along the ground and can sometimes be found in areas that have been recently logged or burned. Thimbleberry (Rubus parviflous) is another great native berry with delicious fruit prized by foragers. The fruits are fragile and do not pack or ship well, so you won’t find them in stores. This makes them an ideal plant to grow at home!
For more detailed information on Himalayan blackberry control, check out the Best Management Practices for Himalayan Blackberry on the WeedWise website at the QR code below. If you have specific questions about Himalayan blackberry or its control, contact the Clackamas Soil and Water Conservation District at 503-210-6000.