Trailing blackberry, Rubus ursinus Cham. & Schlect. spp. macropetalus (Dougl. ex. Hook) Taylor & Mac Bride (Rosaceae)


Trailing blackberry is a low-growing, trailing or climbing, native evergreen shrub growing to 5-6 m in length with densely prickled stems that are greenish-glaucous when young but turn red-brown at maturity.  Leaves alternate, pinnately compound with 3 (occasionally 5) doubly serrate leaflets 3 – 7 cm long. Flowers dioecious, white, up to 4 cm wide and borne in clusters of 2 – 15 flowers on branch ends, fruits red when immature, shiny black when ripe, 2.5 cm long aggregate of drupelets. (1, 3, 7)
NB: The stems of most blackberries are biennial.  Sterile first-year stems, known as primocanes, develop from buds at or below the ground surface and produce only leaves.  Lateral branches, or floricanes, develop in the axils of the primocanes during the second year and bear both leaves and flowers. (7)

©Charles Webber                                              © Tony Morosco




Trailing blackberry grows from British Columbia to northern California and eastward to central Idaho.  It is particularly common from the Cascades to the Pacific Coast extending through southern California into Mexico.  The subspecies macropetalus occurs from British Columbia and Idaho southward into northern California. (1, 3, 7)



Climate, elevation


Sea level to mid elevations in coastal maritime climates and from low elevations to mid elevations in interior continental climates (1, 3, 7)


Local occurrence


Wide spread throughout the Puget Sound basin in all vegetative communities. (1, 3)


Habitat preferences


The trailing blackberry occurs across a wide range of sites from warm, open areas, dense woodlands, prairies, clearings, waste places, and canyons. It can often be invasive in disturbed urban and suburban areas. Trailing blackberry frequently assumes prominence on sites which have been burned or logged and on river terraces or gravel bars dominated by red alder (Alnus rubra). (7)
Trailing blackberry and Rubus spp. in general grow well on a variety of barren, infertile soils tolerating a wide range of soil texture and pH but requiring adequate soil moisture for good growth. Trailing blackberry appears to be tolerant of periodic flooding by brackish or fresh water. (7)



Plant strategy type/successional stage


Trailing blackberry is a vigorous competitor which commonly invades disturbed sites created by logging, fire, or other types of disturbance. It is particularly well represented following catastrophic disturbance in Douglas-fir forests of the Pacific Northwest, and readily established on mudflows and other harsh microsites following the eruption of Mount St. Helens.  Trailing blackberry typically increases rapidly on disturbed sites, persisting until suppressed by canopy closure.  It occurs in stands of all ages but reaches greatest abundance in early seral communities. Although primarily an early seral species, trailing blackberry can sometimes persist in low densities as a residual species in mature forest communities. Trailing blackberry was observed in initial post-disturbance, early immature, late immature, mature, and old growth stands in coniferous forests of southwestern British Columbia.  This shrub increases rapidly and can dominate the herbaceous layer as early as 2 to 5 years after disturbance.  In many western hemlock-western red cedar or Douglas-fir forests of the Pacific Northwest, this shrub remains dominant for at least 20 years after disturbance. Trailing blackberry is present in red alder communities, which on certain upland sites, appear to represent early seral stages of western hemlock forests.  Where these communities occur along streambanks, periodic flooding can maintain species such as salmonberry and red alder in long-lived, disclimax situations.  Trailing blackberry is considered a major dominant in early successional stages of these communities. (7) 


Associated species


Trailing blackberry grows as an understory species with Pacific silver fir (Abies amabilis), Sitka spruce (Picea sitchensis), Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis), western red cedar (Thuja plicata), western hemlock (Tsuga heterophylla), bigleaf maple (Acer macrophyllum), and red alder (Alnus rubra).  Trailing blackberry also occurs in many West Coast riparian communities dominated by willows (Salix spp.) or cottonwoods (Populus spp.) as a codominant with salmonberry (Rubus spectabilis) and thimbleberry (Rubus parviflorus).  Common understory associates include Oregon oxalis (Oxalis oregana), sweetscented bedstraw (Galium triflorum), elderberry (Sambucus spp.), and other blackberries, raspberries, or brambles (Rubus spp.). (7)


May be collected as:


Vegetative: Rooted root crown suckers, rooted branch nodes and semi-hardwood cuttings may all be collected from trailing blackberry for propagation (4, 7)
Seed: (~ 9 x 105 seeds/kg) fruits ripe when black and juicy, July through September. Macerate fruit in water with a blender. Add extra water to float off pulp and nonviable seeds. Several changes of water will yield cleaner seed. (4, 7)
Seedbank:  The seeds of most blackberries remain viable for at least several years after being buried in the soil or duff although the precise length of viability has not been determined for the trailing blackberry. (7)


Collection restrictions or guidelines


Not cited in literature however typical conservative collection methods for genetic integrity and minimal ecosystem impact apply.


Seed germination


Trailing blackberry seeds have a hard, impermeable coat and dormant embryo; consequently, germination is often slow.  Most blackberries require, as a minimum, warm stratification at 86 to 68° F (30 to 20°C) for 90 days, followed by cold stratification at 36 to 41° F (2 to 5° C) for an additional 90 days.  These conditions are frequently encountered naturally as seeds mature in summer and remain in the soil throughout the cold winter months. Laboratory tests indicate that exposure to sulfuric acid solutions or sodium hyperchlorite prior to cold stratification can enhance germination. Sow seed that has been stratified and scarified in the spring can cover with 3 – 5 mm of soil. (4, 7)


Seed life


Not cited in literature however the persistence of Rubus spp. in the soil seedbank for several years might indicate long seed life under controlled conditions.


Recommended seed storage conditions


Not cited in literature however typical low temp, low humidity conditions may apply.


Propagation recommendations


For seed see germination recommendations above. For vegetative propagation rooted semi-hardwood cuttings and stem node pieces should be transplanted as soon as possible to avoid root rot. Otherwise standard vegetative propagation techniques apply. (4, 5, 7)


Soil or medium requirements


None cited in literature. Standard rooting and germination medium probably adequate.


Installation form


Not specifically noted in literature. Well rooted one year old nursery plants or field collected salvage plants or well-rooted branch node sprouts most likely will be successful. Direct seeding in the summer may also work.


Recommended planting density


Suggested planting densities range from 163 to 1100/ha. 50% survival has been reported for large plantings. Trailing blackberry has been promoted as a site stabilizing species and in this case higher planting densities may be preferable. Trailing blackberry is also a vigorous grower and competitor and therefore should probably be planted in very low densities for diversity enhancement. (6, 7)


Care requirements after installed


Not cited in literature but watering transplants during droughty periods is recommended.


Normal rate of growth or spread; lifespan


Trailing blackberry has a rapid growth rate and relatively short life span of unspecified length. (6)


Sources cited


(1)     Hitchcock, C. Leo and Cronquist, Arthur. Flora of the Pacific Northwest. 1998. University of Washington Press, Seattle and London.


(2)     Leigh, Michael. Grow Your Own Native Landscape. 1999. Washington State University Cooperative Extension – Thurston County, WA.


(3)     Pojar, Jim and McKinnon, Andy, eds. Plants of the Pacific Northwest Coast: Washington, Oregon, British Columbia and Alaska. 1994. Lone Pine Press, British Columbia.


(4)     Potash, Laura and Aubry, Carol. Mt. Baker-Snoqualmie National Forest Native Plant Notebook. 1997. North Cascades Institute. Sedro-Woolley WA.


(5)     Rose, Robin, Chachulski, Caryn and Haase, Diane. Propagation of Pacific Northwest Native Plants. 2000. Oregon State University Press, Corvallis.


(6)     USDA, NRCS. 2002. The PLANTS Database, Version 3.5 (http://plants.usda.gov) National Plant Database Center, Baton Rouge, LA 70874-4490 USA.


(7)     USDA Forest Service Fire Effects Information System (FEIS) database. http://www.fs.fed.us/database/feis/plants/


Data compiled by


Rodney Pond 05.24.03