Caragana arborescens, an emerging invasive shrub in Canada’s southern boreal forests

Caragana arborescens Lam. (hence: Caragana ) is an emerging invasive shrub in Canada’s boreal forest, a region formerly considered resistant to biological invasions. Originally introduced to mitigate soil erosion and widely planted as a shelterbelt, hedge, and ornamental, Caragana possesses traits indicative of an ecosystem transformer, including an ability to fix nitrogen, and suppress neighboring plants. It has been reported to spread in natural habitats, yet its general frequency of escape from plantings and rate of spread into natural habitat is unknown. We carried out a field survey in the southern Boreal and Aspen Parkland regions with the aim to (1) evaluate the propensity of Caragana to escape from planted shelterbelt and hedges into natural habitats, using historical shipment records from the Prairie Farm Rehabilitation Administration (PFRA), and (2) calculate its local areal rate of spread based on sites identified through PFRA data and road surveys. We found that in 37 out of 40 sites (92.5%) where bordering on natural habitat, Caragana escaped cultivation. Our field survey reveals a local areal rate of spread of 2.23% per year based on an exponential growth model, and 2.95% per year based on a logistic model, with an average invaded area of 1.98 hectares (± 3.2 SD). Our results provide evidence that when natural habitat is nearby, Caragana escapes from plantations with a high probability. Although its local areal spread is relatively slow, the high density of deliberate plantings implies a high rate of spread at the regional scale. Hence, Caragana represents the first case of a successful woody invader in Canada’s southern boreal forest. Effective management strategies for Caragana would benefit from a better understanding of its habitat preferences, environmental factors influencing local spread, and impact on native plant regeneration and ecosystem functioning.

• Publication year

  2025

• Venue

  BioInvasions Records

• Publication date

  Unknown publication date

• Fields of study

  Not labeled

• Identifiers
  DOI 10.3391/bir.2025.14.4.01
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

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• No concepts are published for this paper.

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