Description

Japanese barberry is a compact, spiny, deciduousa shrub or tree which sheds its leaves annually shrub in the barberry family (Berberidaceae) that commonly grows from 2 to 3 feet tall (although it can grow up to six feet in height). Roots are shallow but tough. The smooth-edged leaves range from oval to spoon-shaped and are clustered in tight bunches close to the branches. The single spines bear small leaves in their axils. Yellow flowers bloom in May, are about one third of an inch wide, and are solitary or in small clusters of 2-4 blossoms. The bright-red fruits mature in mid-summer and hang from the bush during autumn and into winter. The berries are small, oblong, and found singly or in clusters. The plant regenerates by seed and creeping roots. Birds and rabbits are known to eat the seeds and distribute the species. Branches root freely when they touch the ground; thus allowing single plants to become quite large.

Habitat

Japanese barberry is tolerant of a variety of soil types in full sun to shade. Although the species is strongly associated with anthropogenicenvironmental change caused or influenced by people, either directly or indirectly disturbance, this invasive species is capable of establishing under a closed canopy. Japanese barberry prefers well-drained soils, although it has been found in wet, calcareous soilssoils formed from the crushed up and decayed shells and bones of sea creatures, (specifically in a black ash swamp). It is typically found in locations of partial sunlight such as woodland’s edge; it can survive well under the shade of an oak canopy. It is also found along roadsides, fences, old fields, forest edges, and open woods. Japanese barberry can be found invading oak woodlands and oak savannas. Japanese barberry competes poorly with grasses and may succumb to drought conditions. Preferential herbivory on competing shrubs by deer may give Japanese barberry a competitive edge.

History and Introduction

Introduced via the horticultural trade in the late 1800s as an ornamental, Japanese barberry appears to have become naturalized at the turn of the 20th century, after it escaped from intentional plantings in gardens. It is still widely planted today for landscaping and hedges.

Threats

Forms dense stands that compete with native trees and herbaceous plants. It often escapes cultivation. Plants shade out other under-story species. It has the unique ability to change the chemistry of the soil beneath the plant, which in turn makes the site more favorable for additional Japanese barberry plants. Over time, the change in soil pH and the higher nutrient levels can contribute to changes in the whole ecosystem of the area, resulting in a decrease of native plant and animal biodiversity.

Dense stands of naturalized Japanese barberry could result in public health concerns as well. Research in Connecticut and Maine showed that black-legged ticks were twice as numerous in Japanese barberry infestations as in non-invaded areas. Dense Japanese barberry growth creates a microclimate with the ideal humid conditions that ticks prefer. As the carriers of the bacteria that cause Lyme disease, increased tick populations could lead to more cases of Lyme and other tick-borne diseases in humans, pets, and livestock.

Dispersal Methods

Japanese barberry is rapidly spread by birds that eat the berries thus dispersing the seeds.

Japanese barberry is capable of copious seed production, even when light levels are low. In some reports, over twelve thousand seeds can occur on a single plant with upwards of 90% of these seeds germinating. Although the majority of seeds fall within 10 meters of the parent plant, turkey, grouse and other woodland birds have been observed to eat Japanese barberry’s fruit, suggesting the possibility that long distance dispersal is relatively common. This species also spreads locally via rhizome sprouts and layering. Vectors include birds, small mammals and horticultural trade

Control

As with any other invasive infestation complex, large stands of Japanese barberry are best managed via a combination of mechanical and chemical means. Spring wildfires or sequential cutting followed by foliar spray of the vegetation that re-sprouts and/or application of herbicide to cut stumps will give the most complete control. Managed infestations should be monitored for at least five years to ensure exhaustion of the seed bank. Any new seedlings can be hand pulled. Due to Japanese barberry’s ability to alter native soil characteristics, managed sites should be watched carefully for signs of re-invasion from outside sources. 

Mechanical

Mechanical removal of the plant is recommended in early spring because barberry is one of the first shrubs to leaf out, thereby making identification easier. Cutting, pulling or digging are effective in areas where there are only a few plants. A hoe, weed wrench, or mattock should be used to uproot the bush and all connected roots. Thick gloves are recommended for protection from the shrub's spines. Japanese barberry may be relatively easy to control in fire-adapted communities. Fire is thought to kill these plants and prevent future establishment. While mowing will suppress Japanese barberry, it will not eradicate it.

Chemical

Triclopyrherbicide used to control both broadleaf and woody plants has been used as a cut-stump treatment with success. Other herbicides labeled for brush control, such as glyphosatea widely used herbicide that can kill certain weeds and grasses, it works by blocking an enzyme essential for plant growth, may prove to be effective. Care in application is essential because glyphosate is a non-selective herbicide that can kill native species as well. Herbicides are suggested only for plants that are difficult to remove mechanically.