Introduced Species Summary Project
Japanese
Barberry (Berberis thunbergii)
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Common Name: Japanese Barberry 
Scientific Name:
Berberis thunbergii
Classification:
Phylum or Division: Magnoliophyta
-Dicotyledons
Class: Magnoliidae
Order: Ranunculales
Family: Berberidaceae
Identification: Japanese Barberry is a compact woody
deciduous shrub with arching branches.
It generally grows from 2-3' but can get as high as 6-8' in ideal
conditions, forming thick impenetrable thickets. The leaves are small, oval, smooth and untoothed, from 1/2-1 1/2" long. Leaf colors include green, bluish-green to
dark red and purple. The shrub blooms in
the northeastern U.S.
from early April through May with small, 1/4", pale to bright yellow
flowers hanging in clustered umbels from the underside of each stem. These flowers form bright, 1/2" red
berries that persist into late winter.
In autumn the foliage varies in shades from yellow to crimson. The bark is brown with older stems deeply
grooved, growing in a zig-zag form and covered with
very sharp single spines growing from every node. The inner bark is yellow, as are the roots,
and when scraped these parts have a pungent odor. The Japanese Barberry may sometimes be confused
with the Common, or European Barberry (Berberis
vulgaris) which used to be considered a pest in
the 1930s as it colonized open farmland but since second generation forests
have grown up in the northeast, Berberis vulgaris seems to have lost the competitive edge to
Japanese Barberry and itself is no longer considered invasive. There is a native barberry, Berberis canadensis, which grows only in the
southeastern U.S.
and not in Canada
or in New England, the areas where Japanese Barberry is
currently becoming a very serious invasive pest. Whereas all three Berberis
have spiny stems, red berries and yellow inner bark, B.vulgaris
and B.canadensis have toothed leaves as
opposed to the smooth leaves of B. thunbergii, and the spines of the B. thunbergii are usually single and unforked
at each node whereas the spines of B. vulgaris
tend to be double or tripled branched.
Original
Distribution: Discovered
growing in the mountains of Japan
by Russian botanist Carl Maximowicz in 1864 and named
after Swedish botanist C.P.Thunberg (1743-1828).
Current Distribution:
Extends from Nova Scotia south to
North Carolina and west as far as
Montana. Has been reported as
invasive in twenty U.S. States, straight down the eastern seaboard from Maine through North Carolina
and west into Pennsylvania, Ohio, Indiana, Kentucky, Tennessee, Wisconsin and Missouri. B. thunbergii's
progress in the United States
has, to date, been held in check to the south by, probably, its need for cold
winter temperatures for stratification of the seeds, and to the west by,
probably, drought conditions. Although
very drought tolerant once established, a very dry terrain would tend to
discourage its incursion.
Site and Date of
Introduction: In 1875 seeds
imported from Russia
were planted at the Arnold Arboretum in Boston,
Massachusetts. Shrubs grown from these same seeds were
planted in 1896 in the New York Botanic
Garden.
The exotic shrub was apparently regarded as an interesting specimen
plant and there are no records of the species having naturalized in the U.S.
until after 1910, when it began colonizing roadside verges and open pastures.
Mode(s) of
Introduction: By 1920
Japanese Barberry was being promoted by U.S.
nurseries as an attractive landscaping alternative to the European (also known as
"Common") Barberry, B. vulgaris,
which had been brought over by early European settlers to use as hedgerows and
for dyes, jams and medicinal purposes.
European Barberry had itself had become naturalized and, because it was
an alternate host to Black Rust Stem, (Puccinia
graminis) a serious fungus that attacks all
cereal crops, the shrub was actively eradicated by the USDA from farmland in
the 1910s. Because of B. thunbergii's s attractive fall foliage in a variety of
cultivars (there are currently 17 extant cultivars) and the fact it was widely
believed to be unsusceptible to Puccinia graminis, the Japanese Barberry became very popular as
an ornamental shrub, often planted by a doorway or alongside the house. It began spreading from cultivation in suburban
and rural retreats and by the 1960s had dispersed widely and
exponentially. By the 1970s it began to
be regarded as a problematic invasive in the United
States.
The sale of Japanese Barberry was banned throughout Canada
in 1966 but in the U.S.
it is still widely propagated and sold as a problem-free, easy-to-grow
shrub.
Reason(s) Why it has Become Established: Berberis
thunbergii has become naturalized, to the point
of running rampant, in North America for many of the
same reasons that this shrub is still a popular nursery plant. "Rugged, adaptable, no serious problems
or pests, easy to maintain, transplants readily, shade and drought tolerant,
deer resistant" is typical ad copy found at any site offering this shrub
of "colorful fall foliage." Although
it prefers well-drained sites it does just as well in wetlands. It is now found in black ash swamps,
wetlands, open woodlands, pastures, meadows and disturbed areas. The shrub also has a disturbing tendency to
do quite well in the dense shade of forest canopies, such as oak canopies in Wisconsin,
and mixed deciduous canopies of New Jersey
and New York where it can form
dense thickets that prevent the growth of native plant species. It reputedly prefers sun to part shade but
will flower and fruit even in heavy shade.
The shrub is propagated by seed widely dispersed by birds. A rise in populations of the ruffed grouse
and turkey, due in part to the regrowth of second
generation forest, may have much to do with the dispersal of barberry seed,
along with the seed's high (up to 90%) germination rate. Vegetative propagation
is also an option for this adaptable plant.
Any stem that touches the ground can root, as can any bits of root left
in the ground after pulling up a plant.
Because the shrub leafs out very early in spring and maintains its
foliage well after the rest of the forest canopy has dropped its leaves, this
may give B. thunbegrii a photosynthetic
advantage over native plant species as well.
White tailed deer avoid browsing on this plant, which also gives it a
competitive advantage over native species.
The seeds can remain dormant in the soil for over ten years.
Ecological
Role: Originally found in the
mountains of Japan
Berberis thunbergii
served as a forest understory sheltering the forest floor from effects of
erosion while simultaneously providing cover and a food source for birds and
small mammals. Its growth was held in
check in its island biogeography by climate and soil limitations that do not,
unfortunately, operate as restrictively in the wider North American
habitat.
Benefit(s): This shrub serves as a nesting habitat for
birds and cover for small mammals. The
abundant berries that last from fall through much of winter is
a food source, although not a preferred one, for many species of birds. The seeds apparently vary in palatability and
are not very nutritious but if they are the only food source available a bird
will eat them. A useful act performed by
a thicket of Japanese Barberry is that of protecting oak seedlings from deer
browsing. Protected by a briar of thorns
which the white-tailed deer scorn to eat, an otherwise endangered seedling can
get started in life. The plant contains
a substance known as Berberine, an isoquinoline alkaloid, that has a
wide variety of medicinal uses and is much valued in traditional Chinese
medicine and other folk medicine cultures for its antibacterial properties and
is used in the treatment of intestinal symptoms and as a bitter tonic. The roots and stems make a deep yellow
natural dye.
Threat(s): This plant is rapidly displacing
native plant species and creating impoverished monoculture areas. Under forest canopies where it doesn't have
to compete with similar shrubs that need more light, Berberis
thunbergii can form thick stands and displace
native plants, reducing variety in wildlife habitat and forage. Studies done in New
Jersey have indicated that dense stands of Japanese
barberry can change the soil pH and reduce the layer of litter on the forest
floor. This change in soil pH may in
turn aid the spread of Japanese barberry, as well as prevent the regrowth of native species, even after eradication of the
invasive species. It is currently found
to be invasively present in 43 protected forest sites in New
York State. Connecticut
has declared Berberis thunbergii
to be "probably one of the most destructive invasive plants in
CT." The Japanese barberry can also hybridize with the common barberry (Berberis vulgaris) and become
susceptible to black stem rust. For
this reason Canada, although having somewhat relaxed their stringent ban on
Japanese barberry, (under pressure from nursery lobbying), insists on new
cultivars being proven free from black rust fungus, even though it is only a
temporary fix because of the hybridization possibilities.
Control
Level Diagnosis: Highest
Priority. The threat of B. thunbergii as an invasive plant should not be
underestimated. It is not a creeping
vine growing over everything with tropical abundance but it is a highly
persistent competitor with an abundance of advantages over native species. At this point in time eradication may be an
unattainable goal but an organized and coordinated plan of control should be
instituted immediately. The first thing
that should be done is to ban the selling of Japanese Barberry from all
nurseries, as was done in Canada. Nurseries can instead promote native species
such as winterberry (Ilex verticillata),
bayberry (Myrica pensylvanica)
and inkberry (Ilex glabra) all of which have
many of the same attributes of Japanese barberry without the pest's
proclivities.
Control
Method: The best thing is not
to plant Japanese barberry at all.
Gardeners need to be alerted to the invasive dangers of this plant and
nurseries should be offering native species alternatives. For the existent problem, a few options are
available, including manual, mechanical and chemical methods. Small isolated plants can be dug up by hand,
(wear thick gloves) and it is important to remove every bit of root, including
the long taproot, because the plant can regenerate from a piece of root. Because this plant leafs out very early in
spring it is easy to identify and not too difficult to dig a smaller plant out
of the soil when the ground is moist.
For larger plants, (and these shrubs can achieve very large growth, due
to their pattern of stem development and vegetative cloning), a hoe or a Weed
Wrench is most useful and least intrusive on any surrounding non-target
species. Shrubs can be mowed repeatedly,
and will eventually give up the fight to survive, although any seed left in the
soil can remain viable for years so the area must be continuously
monitored. Clipping hedges of barberry
plants in late summer, before they set fruit, can help keep down the seed
dispersal, although there will always be a few berries left hanging because
every arching branch of barberry bears hundreds of flowers. Chemical means such as glyphosate
(e.g. Roundup) and Triclopyr have been used with
success in eradicating large forest infestations of Japanese barberry. Again, because of the species' early spring
leaf out, it is easy to identify and spray carefully before other native
vegetation has grown up. Application in late summer during fruiting is also
considered effective, but must be applied very selectively as glyphosate will kill anything green with which it comes
into contact. There is potential for
biological control of Japanese barberry with the tephritid
fly, which has been shown in Europe to severely reduce
the seed production, but this has not been studied thoroughly in the U.S. Any biological control considered must of
course be studied carefully, lest yet another invasive species be introduced
into a new habitat.
References:
http://www.nps.gov Alien Plant Working Group
- Japanese Barberry
http://www.nature.org/ Nature
Conservancy in Connecticut -
Invasive Plant Fact Sheet/Japanese Barberry
http://www.umext.maine.edu/
Maine invasive plant series Item
#2504 Fact Sheet on Berberis thunbergii
http://www.inspection.gc.ca/
Technical Reference R-004 Japanese Barberry Identification Manual, Canadian
Food Inspection Agency (CFIA)
http://www.centerforplantconservation.org/
this site has a great website listing of everything to do with invasive plant
species in the US
and globally.
http://www.invasions.bio.utk.edu/
Institute for Biological Invasions, University
of Tennessee, run by Dr. Daniel Simberloff. Includes a comprehensive bibliography of literature and fact sheets
on many invasive species.
Ehrenfeld, J.D. 1997. Invasion of deciduous forest preserves in the New
York metropolitan region by Japanese barberry (Berberis thunbergii)
Journal of the Torrey Botanical Society, 124:
210-215.
Ehrenfeld, J.G. 1999. Structure
and dynamics of populations of Japanese barberry (Berberis
thunbergii DC) in deciduous forests of New Jersey. Biological Invasions 1:203-213.
Kourtev, P.S., W.Z. Huang and J.G. Ehrenfeld.
1999. Differences in earthworm densities
and nitrogen dynamics in soils under exotic and native plant species. Biological Invasions 1:237-245.
Silander, J.A. and D.M. Klepeis. 1999. The
invasion ecology of Japanese barberry (Berberis
thunbergii) in the New England
landscape. Biological Invasions 1:189-201.
Photo Credit: http://www.imaginatorium.org/sano/pics/b02937megi.jpg
Author: Eve Harmon
Last Edited: March 27,
2006
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