Before you start cursing Rubus ursinus (variously called Pacific blackberry, Pacific dewberry, trailing blackberry, California blackberry, California dewberry, California grapeleaf dewberry, and Douglasberry) as it tears at your lower extremities whilst walking through forest edges and old clearcuts, you might want to read the extensive list (and by extensive I mean you may want to hydrate first and maybe grab a snack) of the animals that feed on this plant, because it feeds a fair amount of the vertebrate and invertebrate wildlife that you may see, or hope to see, that day.
According to ‘Flora of the Pacific Northwest’ there are 13 species of armed Rubus in our region, and R. ursinus is one of only 5 that are native, and the only native trailing blackberry with thorns. As such it was a very important plant to the indigenous peoples of the region, as well as the native wildlife. Blackberries in general receive a great deal of opprobrium, and as it involves the non-native invasive species, much (some would say all) of it is deserved. But our native Rubus have played a vital role in the environmental evolution of our region, and deserve our respect, which means we need to differentiate them from the invaders. Rubus ursinus is very easy to identify- it is trailing, has thorns and white flowers, and has stems that are greyish, bluish green.
Genetically it is also an important plant in modern fruit rearing- “A cultivar of this species named the ‘Aughinbaugh’ blackberry was a parent of the loganberry. R. ursinus is also a second-generation parent of the boysenberry and the marionberry, or ‘Marion’ blackberry.” https://en.wikipedia.org/wiki/Rubus_ursinus
Ethnobotany– “Berries eaten fresh…Berries pulped and dried for winter use…Fresh or dried vines and leaves used to make a beverage tea…Infusion of leaves taken for stomach trouble…Decoction of root taken for diarrhea…Stems used in purification rituals before dancing…” just some of the 47 entries for this plant on BRIT – Native American Ethnobotany Database, although many of the rest repeat the use of the berries for food. “The vines of trailing blackbery were used by the Saanish Indians of Vancouver Island to place over and under food in steam cooking pits, and also for ritual scrubbing. They and other Coast Salish groups sometimes used the fruits as a purple stain. The berries were eaten fresh, or mashed and dried in cakes, by the Straits Salish, Halkomelen, Squamish, Sechelt, Comex, Nootka, and South Kwakiutt. Other indian uses include: using the leaves and roots to treat diarrhea, dysentary, cholera, excessive menstruation, fever, and sores in the mouth. The leaves of this species also were used as a substitution for tea during the Colonial Tea Boycott. Currently, teas made from this species are recommended by herbalists as a diuretic and mild astringent. In addition, the seeds of drupes all contain Cyanogenic Glycosides. The leaves of Cyanogenic plants were boiled and used as a bitter tonic and astringent, and presently is an ingredient in an assortment of Patent medicines.” Portland State University Northwestern Oregon Wetland Plants Project entry for Rubus ursinus
Description– Stems greyish blue-green (glaucous) and leaves dull on dorsal surface. “Trailing tangles on ground or crawling over logs, stumps in clearcuts. Stems round, vigorous. Thorns recurved, not flattened. Leaves divided into 3 distinct leaflets to 6 in. long, dark green on both sides, toothed, middle leaflet with 3 lobes. Flowers white or pink, more than 1 in. across, borne in clusters. Male, female flowers on separate plants. Blackberries small, longer than wide.” Rubus ursinus | Trailing Blackberry | Wildflowers of the Pacific Northwest
Similar species– Rubus hispidus does not have glaucous stems, and the top of the leaf is shiny; other Rubus sp. are erect or arching, or lack thorns, or have pink to purple flowers.
Habitat– “Grows in streambanks, shrublands, clearcuts, roadsides, burned areas, at low to mid-elevations.” Rubus ursinus | Trailing Blackberry | Wildflowers of the Pacific Northwest
Range– “The plant is native to western North America, found in British Columbia (Canada); California, Idaho, Montana, Oregon, and Washington (Western U.S.); and Baja California state (Mexico).” https://en.wikipedia.org/wiki/Rubus_ursinus ; in our region it is found from the east slope of the Cascades to the Pacific, in sw Oregon/nw California, and at low to mid elevations in the Rockies and their associated ranges.
Eaten by– “California blackberry provides food and cover for many wildlife species [9,14]. Blackberries are eaten by numerous birds, including the ruffed grouse, northern bobwhite, sharp-tailed grouse, California quail, ring-necked pheasant, blue grouse, gray (Hungarian) partridge, band-tailed pigeon, American robin, yellow-breasted chat, pine grosbeak, gray catbird, and summer tanager [3,10,64]. Jays, pigeons, northern mockingbird, sparrows, tanagers, thrashers, and towhees, consume the fruit of California blackberry and nest in its tangled branches . Mammals, such as the coyote, common opossum, skunks, gray fox, red fox, raccoon, squirrels, chipmunks, and black bear, consume the fruit of blackberries…Black-tailed deer feed on the stems and foliage of California blackberry , and in some parts of California it is considered a preferred browse . In the Coast Range of western Oregon, leaves are selected by deer in all seasons except summer, when a wide variety of other foods are present . In many areas California blackberry is particularly important to deer during the fall and winter [12,35]. Deer often feed heavily on the foliage until the leaves are covered by snow . The young leaves, which develop earlier than those of most other associated shrubs, provide an important food source when forage supplies are lowest and deer are threatened with malnutrition . Hines and Land  report that California blackberry browse is a preferred winter food of black-tailed deer inhabiting Douglas-fir (Pseudotsuga menziesii) forests of the Oregon Coast Ranges. In this area it supplied nearly 50 percent of the total deer forage at the beginning of winter. In other winter feeding trials, deer reduced the leaves and twigs of California blackberry by as much as 80 to 89 percent . Elk feed on California blackberry through much of the year in parts of California, although utilization appears to be highest during the fall and winter . Rabbits, porcupines, mountain beaver, and beaver occasionally consume the stems, leaves, and cambium of blackberries [10,64]. US Forest Service’s FEIS entry for Rubus ursinus
“Nectar: Pipevine Swallowtail, Pale Swallowtail, Anise Swallowtail, Clodius Parnassian, Large Marble, Cabbage White, Margined White, Sara Orangetip, Mylitta Crescent, Edith’s Checkerspot (fq), Painted Lady, Western Pine Elfin, Cedar Hairstreak, Green Hairstreak, Johnson’s Hairstreak (fq), Silvery Blue, Northern White- Skipper, Persius Duskywing, Propertius Duskywing, Two-banded Checkered-Skipper, Dun Skipper, Umber Skipper, cf. Adela septentrionella. Recommended nectar plant for Green Hairstreak Corridor project in San Francisco. An important Taylor’s Checkerspot (segregate of Edith’s Checkerspot) nectar plant in British Columbia. Noted as an important nectar plant for butterflies on San Juan Island (Pyle). Pyle strongly suspects it a hostplant for Two-banded Checkered-Skipper on San Juan Island. Geometridae: Dark Marbled Carpet (Dysstroma citrata). Johnson’s Euchlaena (Euchlaena johnsonaria). Lymantriidae: Antique Tussock Moth (Orgyia antiqua). Western Tussock Moth (Orgyia vetusta). Noctuidae: Hitched Arches (Melanchra adjuncta). Western Yellowstriped Armyworm (Spodoptera praefica). Xestia plebeia. Smith’s Dart (Xestia smithii). Sesiidae: Blackberry Clearwing (Pennisetia marginata). Schreckensteiniidae: Blackberry Leaf Skeletonizer (Schreckensteinia festaliella). Tischeriidae: Coptotriche splendida. Tortricidae: Britannia Moth (Acleris britannia). Acleris keiferi. Garden Rose Tortricid (Acleris variegana). Orange Tortrix (Argyrotaenia franciscana).” https://www.cnps-scv.org/images/handouts/CaliforniaPlantsforLepidoptera2014.pdf; in “Leaf miners of North America-2nd edition” (2021) Charley Eiseman lists the larvae of Coptotriche splendida and an undescribed Marmara sp. as mining the leaves of these plants; David Rider’s Pentatomoidea site Plant Host Records List by Host Species, list dozens of species that utilize Rubus sp. as larval hosts, so there must be some that use R. ursinus, though I can find no records of that.
Reproductive timing– Flowers bloom from April to August, depending on elevation and latitude. Fruit ripens in mid to late summer.
Etymology of names– Rubus is the Latin word for blackberry/bramble. The specific epithet ursinus is from the Latin word for ‘bear’, but I was disappointed that I could find no information on what this refers to. If any of my readers knows, I’d appreciate hearing it.
Portland State University Northwestern Oregon Wetland Plants Project entry for Rubus ursinus