Rubus armeniacus, R. bifrons , Himalayan blackberry, European blackberry

This Species Review summarizes the scientific information about fire effects and relevant ecology of Rubus armeniacus and Rubus bifrons in the United States and Canada that was available as of 2020. Both species are nonnative, very closely related, and have similar common names: "Himalayan blackberry" and "Himalayan berry". To avoid confusion, in this Species Review "Himalayan blackberry" refers to R. armeniacus and "European blackberry" refers to R. bifrons . As of 2020, little information was available in the scientific literature on European blackberry despite an extensive search (see FEIS's list of source literature ). Because the two species are very closely related, much of the regeneration, fire ecology, and control information pertaining to Himalayan blackberry likely applies to European blackberry. Himalayan blackberry occurs in many areas of the United States and is invasive in the Pacific Northwest and California. It is considered the most invasive nonnative shrub on the West Coast, where it forms large thickets, displaces native plants, hinders wildlife movement, and causes economic losses. It is most common in mediterranean climates and prefers moist, well-drained soils. It is most invasive in low-elevation riparian, hardwood, and conifer communities. In contrast, European blackberry is not considered highly invasive. Both species reproduce primarily vegetatively via layering and sprouting from rhizomes and root crowns. They also reproduce from seed, which aids establishment on new sites, including burns. The seeds are primarily dispersed by animals. The seeds have a hard coat, are dormant upon dispersal, and form a persistent soil seed bank. Fire or animal ingestion helps break seed dormancy. These blackberries are primarily early-successional, fast-growing species that prefer open, disturbed sites such as streambanks and burns. Himalayan blackberry foliage and litter can be flammable, but Himalayan blackberry may fail to burn on moist sites that lack substantial fine fuels. Himalayan blackberry and European blackberry sprout after top-kill by fire, and they establish from seed after fire. Few studies assessed Himalayan blackberry's long-term response to fire as of 2020, and no fire studies were available for European blackberry. Studies of a single and two consecutive prescribed fires suggest that in the short term, Himalayan blackberry abundance either remains similar on burned and unburned sites or increases after fire. Himalayan blackberry displaces native riparian shrubs by overtopping and outcompeting them for space, light, and nutrients, especially water and nitrogen. It is very difficult to control because its root crown and large, often deeply buried rhizomes can sprout for many years after treatment, and animal seed dispersal provides a ready source of new infestations. Himalayan blackberry is best controlled using a combination of treatments over many years. These may include prescribed fire, mechanical treatments, grazing, and/or herbicides.