Japanese Barberry Guide: How to Control Japanese Barberry

Japanese Barberry (Berberis thunbergii) is a spiny deciduous shrub native to Japan that belongs to the same family as European barberry. It grows in dense thickets with arching branches covered in small, spoon-shaped leaves that turn red in the fall. It also grows yellow flowers and bright red berries. Japanese barberry was initially brought to the United States as an ornamental landscaping plant in the early nineteenth century. Since then, the species has invaded parts, displacing native plants of the United States like Maine, Michigan, Massachusetts, and Connecticut.

Not only does this plant species grow in a variety of soil and climate conditions (thriving in USDA zones 4 to 8; growing in both dry soil and wetlands; thriving in full sun but also shade tolerant) but it also fixes soil to its own optimal conditions. This can create inhospitable environments for other native plants. Japanese barberry has also been linked to the spread of Lyme disease because it is host to large quantities of deer mice.

There are a number of factors that make Japanese barberry an invasive species. Below are some of the reasons why it’s important to control the growth of this plant.

1. 1. It is overabundant. Japanese barberry can easily adapt to different soil types and climates, displacing native shrubs. It can also survive nearly all soil, sun, and climate conditions. It grows just as heavily in natural areas like open woods and pastures as it does in public areas like roadsides and waste lots.
2. 2. It roots easily. Japanese barberry has long, leggy branches, and its understory stems often drop flowers, seeds, and extra stems that quickly root into the ground. This easy germination contributes to the rapid spread of the plant.
3. 3. It has no natural predators. Japanese barberry branches are covered in sharp spikes, protecting them from grazing animals. Deer may attempt to eat the plant, but when they find it inedible they drop the berries, seeds, and pollen on the ground contributing to its dispersal.
4. 4. It contributes to the spread of Lyme disease. Dense thickets of Japanese barberry are often home to large amounts of white-footed deer mice, a species that acts as a larval host for Lyme disease-infected deer ticks.
5. 5. It fixes the soil. By fixing its growing soil to its own perfect conditions, large barberry infestations leech natural resources from the soil. This deprives herbaceous native plants of the natural resources they need to thrive within the ecosystem.

Here is a brief overview of how to identify Japanese barberry in the while.

1. 1. Mind its size. Japanese barberry bushes usually grow to about three feet tall, but can be as tall as six feet in ideal conditions.
2. 2. Look at its branches and leaves. Along the spindly branches of Japanese barberry, there are small, oval-shaped green leaves with single spines that turn reddish-purple in autumn. These leaves typically appear in clusters of six and are spaced out along the length of a branch.
3. 3. Look for yellow flowers. Japanese barberry typically grows small, light yellow flowers adjacent to its leaf clusters.
4. 4. Look for red berries. Japanese barberry fruits are small and bright red, dispersed by birds and deer.

There are a number of ways to help quell the spread of Japanese barberry. Below are some methods of removing and controlling Japanese barberry.

1. 1. Mechanical removal. Mechanical control simply refers to pulling or digging up the barberry plants when they appear. Mechanical removal works best when you’re dealing with small isolated patches of barberry. It’s also a suitable method for barberry clusters in shady areas where they grow shallow roots. Repeated mowing may limit the spread of Japanese barberry, but leaving its roots in the ground allows for the potential for them to resprout. Hand-digging or using a weed wrench is your best option for permanent removal if it is possible for you to do. Resprouting can always occur when the entire root system is not removed from the soil.
2. 2. Chemical removal. For larger and more robust populations of Japanese barberry, herbicide solutions like glyphosate or triclopyr can be helpful when used safely. Before using chemicals to remove Japanese barberry, consider the proximity of the particular site to bodies of water, desirable plants, and native species. In some states, a permit is required to apply herbicide near standing water. For barberry plants that are still growing, apply a foliar (herbicide used on leaves) early in the season.
3. 3. Cut stump treatment. The cut stump treatment is a combination of mechanical and chemical control methods. It involves cutting the plant down completely and applying herbicide to the stump immediately afterward. Herbicide should not be applied to a cut stump if rainfall is expected within four to six hours. The best time to use the cut stump treatment is early spring, at the beginning of barberry’s growing season.

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