Japanese barberry bushes are banned or restricted in a growing number of U.S. states because they’re aggressively invasive, crowd out native plants, and create ideal breeding grounds for ticks that carry Lyme disease. The bans target one species in particular: Berberis thunbergii, a dense, thorny shrub originally imported from Japan as an ornamental plant in the late 1800s. It’s now considered one of the most problematic invasive plants in the northeastern United States.
Which States Have Banned Barberry
West Virginia outlawed the sale or distribution of Japanese barberry starting July 1, 2020, after the state legislature added it to the official noxious weeds list in 2018. Pennsylvania has banned it but allows certain approved sterile cultivars (more on those below). New York prohibits the sale and transport of Japanese barberry under its invasive species regulation, which took effect in 2015. Massachusetts, New Hampshire, and several other northeastern states have similar restrictions ranging from outright bans to mandatory labeling requirements for nurseries.
The trend is toward stricter rules, not looser ones. States that once only required warning labels have moved toward full sales bans as evidence of ecological damage has mounted.
How Barberry Takes Over a Forest
Japanese barberry thrives in conditions that would stress most plants. It tolerates deep shade, poor soil, drought, and deer browsing (deer avoid its sharp thorns). Once established, it forms dense thickets in the forest understory that suppress native plants by competing for light, water, and nutrients.
The damage goes beyond simple crowding. Barberry alters the soil itself, changing pH levels and microbial activity in ways that reduce nitrogen availability for surrounding plants. It also shifts the microclimate beneath the forest canopy, creating warmer, more humid conditions in winter and cooler conditions in summer compared to a normal forest floor. These changes make the environment less hospitable for native seedlings. Research published in Invasive Plant Science and Management found that native tree recruitment drops significantly in forests where barberry has become established, meaning fewer young trees grow to replace older ones.
Birds eat the berries and spread seeds widely, which is how barberry colonizes new areas so quickly. A single bush can produce hundreds of berries, and the seeds germinate readily in disturbed soil, forest edges, and even intact woodlands.
The Lyme Disease Connection
This is the detail that elevated barberry from a nuisance plant to a public health concern. The same humid, sheltered microclimate that barberry creates beneath its dense canopy is exactly what black-legged ticks need to survive. Ticks are vulnerable to drying out, and barberry thickets buffer them from temperature extremes and low humidity that would otherwise kill them.
A study in Connecticut measured what happened when researchers removed Japanese barberry from infested areas. Clearing the barberry and allowing the microclimate to return to conditions typical of native northeastern forests reduced the number of ticks carrying Lyme disease bacteria by nearly 60%. That’s a striking result for a single intervention, and it gave state regulators a concrete public health argument for banning the plant.
In areas where barberry is dense, tick populations can be dramatically higher than in comparable native habitat. The thickets provide not just the right humidity for ticks but also shelter for white-footed mice, the primary reservoir for the bacterium that causes Lyme disease. More mice plus more ticks in close quarters means more infected ticks in your yard and nearby trails.
Sterile Varieties That Are Still Legal
Not every barberry cultivar is banned everywhere. Some states have carved out exceptions for sterile (seedless) varieties that can’t spread through bird-dispersed seeds. Pennsylvania, for example, has approved several specific cultivars developed to be infertile:
- WorryFree series: Crimson Cutie, Lemon Cutie, Lemon Glow, and Mr. Green Genes
- Proven Winners series: Sunjoy Todo and Sunjoy Mini-Maroon
These cultivars were bred at the University of Connecticut specifically to address the invasiveness problem while preserving the compact shape and colorful foliage that made barberry popular with landscapers. If you want the look of barberry without the legal and ecological issues, these are your options in states that allow them. Check your state’s current plant regulations before purchasing, though, because some states ban all Japanese barberry varieties regardless of fertility.
What Happens If You Already Have Barberry
Most state bans target the sale, distribution, and new planting of Japanese barberry rather than requiring homeowners to rip out existing bushes. That said, leaving established barberry in your yard means it will continue producing berries, feeding the spread into nearby natural areas, and providing tick habitat close to your home.
Removing barberry takes some effort because the root system is tough and the thorns make the work unpleasant. Thick gloves and long sleeves are essential. Small plants can be pulled by hand when the soil is moist. Larger, established shrubs typically need to be cut to the ground and the stumps treated to prevent regrowth. For large infestations, repeated cutting over two or three seasons may be necessary.
Native Shrubs That Fill the Same Role
Barberry became popular because it’s compact, colorful, deer-resistant, and low-maintenance. Several native shrubs offer similar qualities without the ecological damage. Winterberry holly produces bright red berries that persist through winter and actually provide nutritious food for birds, unlike barberry fruit, which birds eat but gain relatively little from. Inkberry holly is an evergreen option with a similar dense, rounded shape. Native viburnums, such as arrowwood, offer fall color and berries that support local wildlife. Chokeberry provides deep red to purple foliage in autumn and tolerates a wide range of soil conditions.
Your state’s native plant society or cooperative extension office can recommend species suited to your specific region and growing conditions. Many nurseries that once stocked barberry now carry these alternatives prominently.