To understand the power of invasive plants, it is important to know what makes them tick. In the case of Japanese barberry, Berberis thunbergii, such knowledge might reduce the presence of actual ticks and tick-borne diseases in your environment .  

The connection between this nonnative barberry and Lyme disease may be a surprise. But first, some history. Japanese barberry hails from the Orient and was first brought to this country in 1875 when seeds were sent from Russia to the Arnold Arboretum in Boston. This was not the Russian trickery that we are hearing of today; it was an innocent sharing of botanical resources. From that Boston plant, seeds were distributed to the New York Botanic Garden in 1896.

For almost a century, this plant was a favorite for suburban landscapes, as it is easy to grow, thrives in almost any environment, has persistent leaves and berries, and is deer resistant. It wasn’t much later that folks came to understand its negative role in the environment.  And it was not until 2009 that its sale, importation and distribution were prohibited in Massachusetts, though unfortunately this ban doesn’t extend to some of our neighboring states.

Not only is Japanese barberry a hearty survivor, it is an escapee and easily makes its way into forests, fields, roadsides and wetlands. It outcompetes native plants, creating a monoculture and affecting soil so that other plants can’t easily co-habitate. However, its powers of destruction go even beyond those basics.

Over the last decade, scientists have found an even deeper reason to despair over this pernicious plant. It actually encourages Lyme disease and the ticks that carry it.

Researchers from the Connecticut Agricultural Experiment Station with collaboration from the University of Connecticut discovered interesting and disturbing correlations between the presence of Japanese barberry and the profusion of Lyme disease-bearing ticks. Some startling statistics were found in the study. The study showed that in areas of uncontained barberry, 120 infected ticks per acres were counted, while in contained areas, such as yards, there were about 40 infected ticks per acre. But, in areas without barberry, only 10 infected ticks were found. This is further explained in an article in Scientific American.

Ticks need humid environments, and in fact they will become desiccated if the humidity drops below 80 per cent. Barberry shrubs have dense leaves that retain moisture and even after the leaves fall to the ground they maintain a humid environment — nearly 100 per cent humidity is possible. In the open, ticks can be active 15-16 hours per day, but when protected by barberry, their activities can stretch to 24 hours per day.

Add to that, habitat. The leaf litter below these shrubs can be perfect hideaways for white-footed mice used by larval tick nymphs for a first blood meal. Further compounding the problem is that because deer do not like to eat barberry it infests woodlands even faster, since deer consume the neighboring native plants to the ground and leave the prickly barberry to thrive. And, curiously, one study found that in a forest infected with barberry, there are 12 times more deer than in a natural woodland.

So it seems that the barberry-ans are at the gate. Now that you know the barberry, bug and Bambi connection, make a New Year’s resolution to rid your yard of Japanese barberry.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.