The Minnesota Department of Agriculture’s recent Weed of the Month is more than just noxious. It also is a prime hiding spot for ticks.
Japanese barberry (Berberis thunbergii) is a specially regulated plant on Minnesota’s Noxious Weed list. The sharp spine-covered shrub, which grows 3 to 6 feet tall, is a prime housing location for deer ticks, according to researchers in Connecticut. They found higher densities of deer ticks carrying Lyme disease in barberry infestations than in other habitats. Why? Because Japanese barberry infestations offer an ideal, humid environment for the blood-sucking pests.
According to MDA, Japanese barberry was initially introduced to the U.S. as an ornamental and landscape plant. Since the 1980s, it has been found naturalizing in wooded areas. The shrubs will grow equally well in full sun or deep shade. Its small, round leaves are borne in clusters along the stem. Small yellow flowers in summer turn to reddish-orange oblong berries which dangle from the leaf nodes. The landscaping cultivars have highly variable leaf coloration — including purple, green, gold and lime green. However, no matter their provenance, the escaped, naturalized plants will always have green leaves in summer, which turn red or orange only in fall.
Deer do not eat Japanese barberry because of its sharp spines. However, birds ingest the fruit, thereby facilitating its spread. Barberries have the ability to change the soil chemistry beneath the plant, making the site more favorable for further infestation. Thanks to its ability to root from stems, Japanese barberry can form thick, impenetrable thickets.
Deer are only one vector for ticks. White-footed mice and other rodents are important vectors for immature ticks and are the primary sources for a tick larva’s first blood meal. Mice thrive in stands of Japanese barberry. The dense, impenetrable stands protect them from predators and provide optimal nesting sites, according to MDA.
To get rid of barberry, MDA weed specialists suggest cutting, pulling or digging small infestations. When disposing of plants, make sure the roots are exposed and will dry out to prevent them from rerooting. You can also bag or burn the removed plants, or apply foliar herbicide. However, this is often an expensive way to control large infestations. You also might want to consider a prescribed fire if you have a large stand of it.
MDA weed scientists point out that Japanese barberry outcompetes and displaces native plants and restricts movement of wildlife, humans and livestock. Combatting ticks and tick-borne disease is another compelling reason to prevent and control barberry shrubs. To learn more about identification and control measures for Japanese barberry, visit MDA’s website, bit.ly/2ilqQ5Z.
If you find this plant naturalizing, report it by calling the Arrest the Pest at 888-545-6684 or emailing firstname.lastname@example.org.