Himalayan blackberry

Rubus discolor

Background

Identification

• Arching stems, green to reddish purple, 1/4 to 3/4 in. thick, deeply angled (not round in cross-section).
• Flowers white to pinkish, 1 in.
• Spines are subtly curved, thick, most with wide bases, unlike native blackberry (Rubus ursinus) whose spines are straight and thin.
• Leaf generally with 5 separated leaflets, sharply toothed edges, whitish on underside; native blackberry leaf always has 3 leaflets.

Identification key in: Hickman, J. ed. 1993. The Jepson Manual: Higher Plants of California. University of California Press.

Growth and spread

• Seeds are well dispersed by wildlife feeding on the ample fruit.
• Arching stems that contact ground root and create daughter plants.
• Root and stems pieces often resprout.

Habitat and local distribution

• Disturbed moist areas, roadsides.
• Needs lots of sun.
• Native to Eurasia, very common throughout Bay Area.

Impacts

• Creates dense thickets, impenetrable due to sharp spines; crowds out native plants.
• Favored by rats for food and shelter (Hickman 1993).

Prevention and Control

Prevention

• Plant natives or spread native seed in disturbed areas.

Manual or mechanical control

(Hoshovsky 2000)

• Mechanical cutting of canes—not viable method alone since roots will resprout.
• Hand digging and removal of roots—time-intensive but effective, especially for small infestations; however, all root fragments must be removed to prevent rapid resprouting.
• Mowing or hand trimming—requires several trimmings to deplete food supply; optimal time is at beginning of flowering period; roots may resprout.
• Estimated costs: vary depending on if volunteers conduct removal and on the plant density; equipment costs range may from $100 to over $1,000 (Gibbons et al. 1999). There may be additional fees for disposal of plant material.

Biological control

• Biological control agents—none have been approved by USDA due to the potential risk to the commercial species (Hoshovsky 2000).
• Grazing—goats have been used in California to control spread of species (Daar 1983).

Chemical control

• Application of herbicides—glyphosate (as Roundup®) effective when leaves are young and actively growing, not when plants have been recently cut; apply evenly to leaf surface until wet, however dripping herbicide will harm other grasses and shrubs; triclopyr works better in lawn areas since it is not as harmful to most grasses (DNRP 2000).
• Estimated costs: costs for materials and application by a contractor are approximately $250 per acre for glyphosate, depending on size of treatment area, scale of treatment, and herbicide dosage. It is recommended to contract a licensed professional for herbicide applications (Gibbons et al. 1999).

References and more information