Japanese barberry (Berberis thunbergii) is an invasive shrub from Asia. Invasives are species not native to our country or state and can cause ecological, economic or human harm. They arrive here as a result of international trade and intentional or accidental release. Outside of their native ranges, they lack predators or other factors that keep them from out-competing, or overcoming native species. Invasive species have been shown to degrade habitats and cause declines in native plant and wildlife populations. They can cause the loss of crops and income, and can also affect recreational opportunities in addition to other species. The United States spends billions of dollars a year in efforts to control invasive species and reduce their impacts.
Japanese barberry was introduced in the 1870’s for landscaping, and was used extensively for hedgerows and prized for its attractive red berries and bright red fall foliage. It is a dense spiny shrub (you might know it as a “pricker bush” that is common in neighborhoods and farms). They can grow up to 8 feet tall, have zig-zag branches and small oval leaves that range from green to purple in the summer, with white to yellow flowers.
Barberry can produce large numbers of seeds at a rapid rate and tolerate a variety of conditions –which are typical of invasives. It escapes from gardens and farms and can crowd out native plants, which threatens native biodiversity and normal ecological functions in forest, field and edge habitats. Wildlife help barberry spread by eating the berries and dispersing the seeds in their scat (poop). Studies have shown that these berries have less nutritional value for wildlife than native fruits such as native cherry or viburnums. Barberry grows into dense thickets, crowding and shading out native plants and seedlings, reducing habitat and forage for other species. Additionally, barberry has been found to alter soil pH and the layer of vegetative litter on the ground. This change in soil pH can persist long after the invasive has been removed, further inhibiting native plant growth. It poses a threat to humans as well by creating prime habitat for deer ticks, which can transmit Lyme disease.
A simple control method for established Japanese Barberry plants is to dig them out. Barberries are fairly shallow-rooted and typically easy to dig out, but all of the roots must be removed to prevent regrowth. The roots are easily identified by their yellow color when broken. Once dug from the ground, the shrub should be disposed of in a manner that leaves it dead and unviable. This can be done by burning, chipping or leaving the plant in the open sun to desiccate. Plants may be bagged in thick heavy bags, such as contractor bags, and thrown out, particularly if berries are present to avoid establishment of new plants.
For very large shrubs or thickets where manual or mechanical removal may not be feasible, systemic herbicides may be used with a basal bark (spraying the entire circumference of the lower trunk or stem of the plant) or cut stump application. Chemicals are recommended as a last resort and should be applied by a licensed applicator. It is advised that people carefully follow label instructions to minimize impacts on native species.
Though new regulations prohibit planting of Japanese Barberry in New York State, it is still sought as a landscape shrub because deer do not eat it, it is hardy (further traits of invasive species), and the red phase offers a pleasing color to gardens. Thus, established barberry plants continue to threaten native ecosystems and efforts to control invasives.
There are native deer-resistant shrubs that could be planted in place of this invasive, such as St. John’s Wort, Highbush cranberry, Winterberry, and Shrubby cinquefoil. You can consult native plant nurseries and other sources, but also check the New York Flora Atlas to make sure the shrubs are native to New York State.
The simplest precaution that can be taken to control invasive Japanese barberry is to increase awareness of it and plant only native plants in gardens. This helps to support native plant species and the wildlife and native pollinators that rely on them. You can also look for volunteer opportunities in your local State Park for invasive species removal workdays in the spring to fall.
Going Native: Invasive Species
New York State Prohibited and Regulated Invasive Species Regulations
Post by Amy McGinnis, State Parks