October Weed of the Month: Himalayan Blackberry

Home Weed-of-the-MonthOctober Weed of the Month: Himalayan Blackberry

October 3, 2025• Weed-of-the-Month• Samuel Leininger

The Thorn in Our Side

Himalayan blackberry (Rubus armeniacus) attracts a lot of attention with its sweet fruit in the summer but the rest of the year, it tortures us its prickly vines. Also known as Armenian Blackberry, this widespread and aggressive noxious weed is native to Armenia and Northern Iran. It is considered an invasive species in many parts of the world, including here in Clackamas County.

In Oregon, Himalayan blackberry is a widespread Class B noxious weed. It is found in much of western Oregon and is very common weed of economic importance. As a state-listed noxious weed, the propagation, transport, and sale of this plant is prohibited.

Himalayan blackberry thrives on unmanaged sites, disturbed areas, and along stream corridors. This weed is commonly spread by birds, and is also commonly found under perching sites, such as along fence rows and under power lines.

Himalayan blackberry is a tall, semi-woody shrub with thorny stems and edible fruits. It grows upright on open ground and will climb over uneven terrain 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.

Himalayan blackberry forms dense, nearly impenetrable thickets of brambles. In some instances, canes can reach densities of more than 100 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 Blackberry?

The removal of blackberry from public and private property is an ongoing battle. The plant aggressively reproduces by seed which passes undamaged through the digestive tract of many birds and animals and can remain dormant in the soil for several years. The canes of adult blackberry plants will also root where the tips touch the ground. Roots may reach 30 feet in length and extend 2-3 feet deep. Unfortunately, even small root fragments can develop into new plants.

Management of invasive blackberries requires the investment of significant time, equipment, and labor. In the case of agricultural and natural resources lands, infestations by blackberry can reduce the quality and availability of land for farming and natural resource production. This can significantly reduce production and increase costs. Rising costs are then passed on to consumers through increased prices of food and natural resources.

Habitat for wildlife is also disrupted when blackberries form dense thickets that 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 also serve as fuel for wildfires.

How Can I Control Blackberry?

Autumn is an ideal time to manage Himalayan blackberry 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 co-exist with blackberry are also actively growing during the spring and summer months, so control activities on blackberry during this time can potentially do more harm that good.

In the fall months, many of our native plants have largely died back or become dormant for the season, young birds have fledged, and the blackberry flowers and fruits are no longer attracting wildlife. At this time, blackberry plants are also 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 herbicides, ALWAYS READ AND FOLLOW THE LABEL to reduce risk to you others.

For manual control, it is important to arm yourself against the sharp thorns by wearing thick gloves, sturdy long pants, and long-sleeved shirts or jackets. Those who are unprepared will suffer the consequences with nasty scratches. Use a board or plywood to mash down blackberry canes to access densely infested areas. If your ground is level or has little to no slope, you may also be able to cut or mow down the canes to remove the bulk of the plant.

If you wish to use the mowing method for permanent control, you will need to repeat this process throughout the year and for several seasons to exhaust the energy in the root system. Remember to check for any nesting birds in the spring.

Goats can also be used to manage blackberries. Goats are effective at defoliating blackberry plants, but will leave the woody canes behind. As a result, you may still need to remove old to allow access and improve management.

If you choose to remove the entire plant, including the roots, you will have much easier access with the top growth removed. Digging or tilling can take out the root system, but be sure to remove as much root material as possible. Even small pieces can re-sprout, so care needs to be taken to remove any root fragments. If you are working on a slope, make sure you have enough time in the fall to reseed any disturbed areas to avoid erosion caused by late season rains. If not, root removal might need to wait until spring.

After blackberry is removed, expect a flush of weeds in the old blackberry patch. A build-up of weed seed may remain dormant under the brambles for years and may germinate once exposed to additional sunlight.

Removal of invasive blackberry requires persistence and patience, but success comes to those who persevere! For more detailed information on blackberry control, check out the Best Management Practices for Himalayan Blackberry. If you have specific questions about Himalayan blackberry contact the WeedWise program.

If You Like the Berries, Plant a Native Instead!

There are many berries native to our region, that are much less aggressive and yield tastier fruit. Within the WeedWise program, one of the most prized berries is Whitebark Raspberry (Rubus leucodermis). Also know as blackcap raspberry, this native shrub yields a complex fruit, with earthy undertones than the often astringent Himalayan blackberry. It is also characterized by a strikingly handsome blueish color to its stems.

Pacific blackberry (Rubus ursinus), also known as trailing blackberry, wild mountain blackberry, or Northwest dewberry is the only native blackberry 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 parviflorus) 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 eat on the trail or grow at home!