Editor’s note: Summer is time for blackberries ripening along trails, roadsides, and streams around the Salish Sea region. Whether you’re snacking on blackberries during a casual walk or out on a serious berry-picking expedition, knowing something about these plants’ ecology and history will enrich your experience. Read on for an introduction to our local blackberries and their cousins.

Blackberries are a culinary delight; however, they can also be an ecological fright. Three species of blackberry grow around the Salish Sea. Trailing blackberry (Rubus ursinus) is a native treat, but the other two, Himalayan blackberry (Rubus armeniacus) and evergreen blackberry (Rubus laciniatus), are non-native and invasive species with a tendency to take over.

Blackberries are in the rose family (Rosaceae) and the genus Rubus. Blackberries, along with their Rubus siblings, produce compound berries. A compound berry, also called an aggregate fruit, is made up of individual drupelets that are like mini berries. The flowers of Rubus species have multiple carpels, the female reproductive structure. When fertilized, each carpel produces a drupelet with a seed. Since all the carpels are part of the same flower, the drupelets are all connected into a single berry.

Blackberries and raspberries are both part of the Rubus genus and can be difficult to tell apart. A key difference is how the berries detach from the stem. When plucked, a raspberry pulls away from its receptacle (the part that connects the berry to the stem) leaving a hollow berry, which makes an excellent hat for little fingers. The receptacle of blackberries, however, comes off with the berry, and leaves it filled like a stuffed olive. All three blackberry species develop white to pink flowers from April to June. Their berries ripen in mid to late summer.

Trailing blackberry on pavement. photo by Thomas Noland

Closeup of trailing blackberry leaves. photo by Sarah Ottino

Five-leaflet cluster of Himalayan blackberry. photo by Sarah Ottino

Himalayan blackberry is native to the Caucasus region of Eurasia. It was intentionally introduced to the East Coast of the United States in 1885 by Luther Burbank and became established on the West Coast by 1945. Himalayan blackberry has erect canes that grow straight up then arc back toward the ground as they lengthen. The prickles of this species are stouter than those of the trailing blackberry. Its leaves are toothed and tend to be evergreen, though not always. They grow in clusters of three to five leaflets. Young leaflets tend to be more pointed, but mature leaflets are often oval.

Deeply lobed leaves of evergreen blackberry. photo by Sarah Ottino

similar species

The leaves of evergreen blackberry with their lace-like appearance are easily distinguishable. However, Himalayan blackberry and trailing blackberry can be confused with other Rubus species. When sporting only three leaflets, Himalayan blackberry can be confused with trailing blackberry as well as the native salmonberry (Rubus spectabilis). If the plant has upright growth, as opposed to vine-like growth, trailing blackberry can be ruled out.

To decide between Himalayan blackberry and salmonberry, flower and berry color can be good indicators. Blackberry flowers are white or light pink, while salmonberry flowers are vibrant pink. Ripe salmonberries are yellow-orange or red, while ripe blackberries are black. Finally, looking at the surrounding area for mature plants can also be helpful. If the area has a thicket of mature salmonberry nearby, there is a good chance that the young shoot is also a salmonberry.

Blackcap raspberry (Rubus leucodermis) is another blackberry lookalike that is native to the Salish Sea region. It has groups of three leaflets that are white on the underside. It has glaucous stems like trailing blackberry, but it has upright, arching canes like Himalayan blackberry.

Identification of Rubus species is not always easy. Cross-pollination between species is not uncommon, and the amount of sun an individual plant receives can impact its coloring and growth form. While each species has some distinguishable characteristics, not every plant displays them.

blackberry ecology

All three species of blackberry in the Salish Sea region have ecological roles. They develop flowers that are appreciated by insect pollinators, produce berries that are devoured by both birds and mammals, provide cover for smaller animals, and reduce erosion on hillsides.

The three species all reproduce via seeds. The two non-native species can develop seeds with or without fertilization of the flowers (asexual seed production is called apomixis). They can also reproduce vegetatively, with stem tips and fragments developing roots and sprouting new canes. Their fast growth and success at reproducing allow these three blackberry species to quickly take over disturbed sites, forming a monoculture.

While trailing blackberry can consume an open area, its growth is less aggressive than its invasive relatives. Trailing blackberry’s vine-like growth stays lower to the ground, allowing taller species to survive around it. The non-native Himalayan blackberry and evergreen blackberry form dense thickets several feet high. Their arching canes engulf streams, creating barriers for wildlife, and overtake neighboring plants, including trees. While a monoculture of blackberry plants can benefit a few species, a landscape rich with species diversity is healthier. Biodiversity is vital for keeping water and air clean, as well as helping mitigate the effects of natural disasters and disease outbreaks. 

battling the invaders

Due to their aggressive growth, both Himalayan and evergreen blackberries are listed as Class C noxious weeds in Washington State. Since both species are widespread, control and removal is encouraged but not required by law.

Himalayan and evergreen blackberry are hardy and take time to eliminate. Gardeners with a blackberry infestation have a battle ahead of them, but all is not lost. Repeated mowing, cutting, or goat grazing of fresh shoots, combined with the removal of root balls, will eventually lead to success, though the process may take several years. As land is reclaimed, adding mulch and planting new species will help prevent blackberries from once again dominating.

As the climate changes, aggressive plants such as invasive blackberries are more likely to outcompete other plants. Himalayan blackberry has a high tolerance for different water, light, and soil conditions, which allows it to grow in areas where more sensitive native plants cannot. As the climate changes, increases in wildfires will create disturbed areas for Himalayan blackberry to grow, and changes in rain patterns may be less impactful for this species.

As humans, we can opt to remove invasive plants from private property and replace them with natives. We can also join work parties to help public lands recover. Finally, going out blackberry picking can be a fun and delicious activity that keeps a few seeds from getting the chance to sprout.

Evergreen Blackberry | Burke Herbarium

Evergreen Blackberry | WA Noxious Weed Control Board

Himalayan Blackberry | Burke Herbarium

Himalayan Blackberry | WA Noxious Weed Control Board

Trailing Blackberry | Burke Herbarium

Salmonberry | Burke Herbarium

Blackcap Raspberry | Burke Herbarium 

Fire Effects on Rubus Armeniacus | US Forest Service

Rubus Armeniacus (Himalayan Blackberry) Occurrence and Growth in Relation to Soil and Light Conditions in Western Oregon

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