Japanese Barberry: a prickly, tickly topic
By LIAM OLIVER and DR. SIGRID RESH
Are you trying to select your landscaping plants for next year? Here’s why you should avoid Japanese barberry (Berberis thunbergii) and its cultivars. Japanese barberry is a common woody ornamental plant that might be planted in your yard right now and is probably being sold at some local nurseries. Unfortunately, it doesn’t stay only where it was planted; it is an invasive species that is prevalent in our area, especially in forests near landscaped properties.
Invasive species are species that are non-native to a given area, and whose introduction can cause harm to the environment, economy, and human health (Executive Order 13751). With no natural predators, competitors, or diseases where it has been introduced, it replaces native vegetation and provides limited resources to our wildlife, especially specialists.
Japanese barberry becomes detrimental to the environment when it is spread by birds and mammals from yards into neighboring forests, where it takes root in our forests and woodland edges, eventually creating a near monoculture of the invasive plant. In 2018, Link et al. showed that barberry lowered native tree seedling densities by more than 80% when compared with those of uninvaded sites, with predictions of long-term consequences for forest ecosystems.
It not only negatively impacts ecosystems, but it also puts our families, even our furry companions, at higher risk of Lyme disease, which is caused by deer or blacklegged ticks (Ixodes scapularis) carrying the bacteria, Borrelia burgdorferi. Williams and Ward (2010) conducted research that showed that the populations of blacklegged ticks had doubled in ecosystems dominated by Japanese barberry compared to those of areas where barberry was removed.
According to the researchers, this is because Japanese barberry provided a humid microclimate more suitable for ticks, helping them to survive and reproduce even during drier conditions.
Despite its many cultivars, Japanese barberry is easy to identify. It is a spiny shrub that can grow up to three feet tall. Its leaf colors are variable (from green to red to purple) but its small, alternate, spoon-shaped leaves, which appear to circle the stem, are very characteristic. It has yellow flowers in the spring that hang all along the stems and develop into small, bright red, oblong berries in the fall.
To help reduce the spread of barberry in our area, you can dig it up, removing all of the larger roots, and replace it with a native species. Some recommended native replacements are species like Black chokeberry (Aronia melanocarpa), Winterberry (Ilex verticillata) or Ninebark (Physocarpus opulifolius). For more suggestions go to Woody Invasives of the Great Lakes website (https://woodyinvasives.org/). These native species alternatives provide food and habitat for native insects and the food webs they support. To learn more about Japanese barberry visit https://www.michigan.gov/invasives/id-report/plants/shrubs/japanese-barberry or to get involved locally contact firstname.lastname@example.org or visit KISMA’s website at https://www.mtu.edu/kisma/.
Liam Oliver is an undergraduate at MTU. Dr. Resh is the coordinator for the Keweenaw Invasive Species Management Area