Blackberries have become a sign of summer in the Pacific Northwest, and it is not uncommon to spot the delighted traveler stopped on the side of the road happily gathering a bounty to make their next jam or pie. However, for those of us working in the field, there are few sights less pleasant than a stand of impenetrable blackberries. Field crew first aid kits are well stocked with Band-Aids thanks to this invasive shrub. Unfortunately, the Himalayan blackberry, with its delicious berries and vicious thorns, is invasive to the Pacific Northwest.
Native relatives include the trailing blackberry (Rubus ursinus) and salmonberry (R. spectabilis). The trailing blackberry is much smaller than the Himalayan blackberry, growing only 2 to 5 feet high, and usually have 3 leaflets. Trailing blackberries, although similar in color and shape, are slightly smaller. Salmonberry are shrubs that grow 1 to 13 feet tall with woody stems covered with fine prickles. Salmonberry leaves contain 3 leaflets with toothed leaf margins. The pretty pink flowers develop into berries that resemble large shiny yellow to orange-red raspberries.
The Himalayan blackberry is a rambling perennial, woody shrub with thick, corrugated stems (like a pencil) and stiff, hooked thorns. The stems, also called canes, can reach up to 40 feet and root at their tips when they arch over and touch the ground. The entire shrub may grow up to 15 feet and form dense thickets that are daunting to even the most experienced field crews. The leaves are alternately arranged on stems. Each compound leaf composed of 3 to 5 leaflets, with 5 being more common, and toothed margins. The white- to rose-colored flower clusters are flat-topped and have 5 to 20 flowers about 1 inch in diameter. The flowers form blackberries ranging in size from ½ inch to 7/8 inch. A single berry can contain up to 80 seeds that can spread by mammals, birds, and water.
A fan of the disturbed area, the Himalayan blackberry is often found in vacant lots, railroad right of ways, degraded riparian areas, fence lines, and electricity power transmission lines. The plant grows aggressively, more than 20 feet in one year, causing harmful environmental and economic impacts. Himalayan blackberries out-compete low growing native vegetation through shading and rapid build-up of leaf litter and dead stems. The blackberry spreads quickly to claim large areas, limits the movement of large animals, and takes over stream channels and stream banks. The Himalayan blackberry is also attracted to watercourses and creates sites of erosion and flood risk by overthrowing deep-rooted plants.
The name is a bit of a misnomer, as the shrub originates from the Armenia region (hence the scientific name, Rubus armeniacus), and is now distributed worldwide. Within the U.S., it is concentrated mainly along the west coast, although it also occurs along the east coast and in Hawaii. The berry has a somewhat twisted tale on how it was introduced to the Pacific Northwest. The Himalaya Giant, which later became the Himalayan blackberry, started out as an experiment by Luther Burbank in the 1890s to create a thornless version of this plant. Unfortunately, as I and many other field scientists can attest, it maintained the thick, hooked thorns that are all too eager to latch on for a taste of our blood, hair, or clothing.
Control of this aggressive and widely-spreading weed is incredibly difficult and often requires at least 2 years of dedication to substantially eradicate. The Washington State Noxious Weed Control Board recommends labor intensive mechanical control (repeatedly digging out root crowns, repeated removal of above ground growth several times a year, and repeated burning); my favorite – the biological control uses grazing goats (however this only serves to temporarily stop the plants from spreading and does not eradicate them); and herbicide control.
Now, if only Herrera had a team of goats ready to assist with our summer field work…