In the plant world, green is good, right? Most of the time. The exceptions are those insidious invasive species. Typically, these are plants introduced to the United States from Europe or Asia as landscape plants. Japanese barberry (Berberis thunbergia) is an example of a well-intentioned idea that went awry. Imported in 1875 for use as living fence for livestock and herbal medicines, it appealed to homeowners due to its attractive light green, yellow, or purple foliage, bright red berries, and ability to be shaped into a hedge.
Invasive plants are called invasive for a reason. They outcompete our native trees, shrubs, and herbaceous plants, choking out those that best sustain our native wildlife. They reproduce prolifically and are tolerant of a wide range of soil types. The plants are highly adaptive to different growing conditions. Japanese barberry exhibits many of these characteristics. For more than 100 years it has been spreading mayhem in parks, forests, wetlands and yards. Barberry is quite hardy and can populate areas of full sun to deep shade. It is drought tolerant and can also be found in wet areas. The bushes produce pretty fall berries but they are not a preferred food source like our native dogwood shrubs, buttonbush and American hazelnut. The seeds are not particularly nutritious for wildlife; however, they are eaten and deposited everywhere via wildlife droppings, quickly expanding to new locations. In addition to the high seed production and distribution, the plant also reproduces horizontally, a process called layering. Where branches contact the ground, roots will form, creating new bushes. All of these attributes mean that the plants can quickly outcompete native plants, including our lovely spring wildflowers and valuable timber trees. To add insult to injury, the stems are covered with vicious spines that are as sharp as a hypodermic needle.
But what is most offensive is the relationship of Japanese barberry to ticks. Researchers at the Connecticut Agricultural Experiment Station, with participation from the University of Connecticut, found higher populations of deer ticks (also known as blacklegged ticks) where Japanese barberry was present. The dense foliage of the barberry retains a greater amount of humidity, which ticks really like. The brutal thorns of the barberry mean white-footed mice enjoy a safe haven from predators. Tick larvae feed on the white-footed mice, which are known reservoirs for Lyme disease. Infected larvae metamorphose into nymphs which feed on humans, pets, or other animals. The cycle continues as nymphs morph into adults whose meal tickets are usually white-tailed deer. Even though deer are not good reservoirs for Lyme and other tick-borne diseases, they serve as a tick taxi. Adult female ticks hitch onto a deer to feed and then drop off once engorged with blood.
An excellent resource to learn about Japanese barberry can be found at Buckeye Yard and Garden Online (https://bygl.osu.edu/index.php/node/1726). If you have barberry, learn how to eradicate it and find a suitable native preferred alternative. The Ohio Invasive Plants Council has a list of alternatives to invasive species, including Japanese barberry, which can be found at https://www.oipc.info/uploads/5/8/6/5/58652481/alternatives_to_ohio_invasive_plant_species.pdf. If you are a woodland owner, don’t wait to implement treatment because high seed production and layering will allow barberry to rapidly broaden its reach. The USDA Natural Resources Conservation Service offers technical and financial assistance for voluntary conservation measures through its Environmental Quality Incentives Program. Visit https://www.nrcs.usda.gov/wps/portal/nrcs/oh/home/ to discover more and see if your woodlot qualifies.