Japanese barberry: Invasive Species?

When discussing invasive species, the wicked inconvenience of cultivars will quickly arise, especially when focused on the genus Berberis. One species, Berberis thunbergii, has established itself as a poster child for garden favorite gone wild. And yet there is some suggestion from professional gardeners and horticulturists that suggests that there are cultivars and varieties which are not invasive. Berberis thunbergii 'Aurea', Berberis thunbergii 'Bonanza Gold', and Berberis thunbergii 'Gold Nugget' are but a few of the ornamental cultivars in the horticultural trade.[1] And these cultivars along with others raise questions which go to the heart of the invasive species controversy.

“Japanese barberry was introduced to the United States as an ornamental in 1875. Seeds were sent from Russia to the Arnold Arboretum in Boston, Massachusetts. In 1896, it was planted at the New York Botanic Garden. It was eventually promoted as a substitute for Berberis vulgaris, an exotic plant introduced and used by early settlers from Europe for hedgerows, dyes and jams, and later found to be a host for the black stem rust of wheat.” [2] “In the United States, Japanese barberry occurs throughout much of New England and the Northeast, south to North Carolina and west to Michigan and Missouri. Barberry forms dense stands in a variety of habitats, including closed canopy forests and open woodlands, wetlands, pastures, meadows and wastelands. This highly shade-tolerant exotic shrub displaces a variety of native herb and shrub species in areas where it is well established. [3] Japanese barberry forms dense stands in natural habitats including canopy forests, open woodlands, wetlands, pastures, and meadows and alters soil pH, nitrogen levels, and biological activity in the soil. Once established, barberry displaces native plants and reduces wildlife habitat and forage. White-tailed deer apparently avoid browsing barberry, preferring to feed on native plants, giving barberry a competitive advantage. In New Jersey, Japanese barberry has been found to raise soil pH (i.e., make it more basic) and reduce the depth of the litter layer in forests.” [4] This last piece of information may be shown to work in conjunction with non native earthworms to allow adventitious exotic species to more easily displace native plants, and allow the creation of biological deserts, or mono-cultures.

It is important to keep in mind the distinction between variety and cultivar. “Variety names are given when the mutation occurs in nature. (Eg a mutation occurs in a wild arid land) B. The abbreviation var. is used to signify that the mutation is a variety. var. is placed after the specific epithet and is not underlined or italicized.”, whereas “Cultivar names are given when the mutation occurs due to human influence. Examples: a mutation occurs in a green house. B. The abbreviation cv. is used to signify that the mutation is a cultivar. cv. is placed after the specific epithet and is not underlined or italicized.” [5]

Berberis thunbergii var. atropurpurea 'Angel Wings', Berberis thunbergii var. atropurpurea 'Crimson Giant', Berberis thunbergii var. atropurpurea 'Crimson Pygmy', Berberis thunbergii var. atropurpurea 'Crimson Velvet', and Berberis thunbergii var. atropurpurea 'Rosy Glow'[6] are important varieties in the garden industry. These cultivars and varieties have important uses as described, interestingly enough, by work done at the University of Connecticut: “Landscape Use, such as for: borders and hedges; Groupings (sic) and mass plantings; in urban areas. difficult sites; yellow, red and variegated foliage forms to add color to a landscape.”[7] In addition, barberry is used to counter the ravages of deer in the eastern United States. “Begin with a selection of deer resistant plants such as: Abies, Amelanchier, Berberis, Buxus, Cornus vars., Ilex glabra, Magnolias, Picea abies, glauca & Pungens, Pieris japonica, Pinus mugo & nigra, Spirea & Syringa to name a few. Plant these plants in front of favored plants…”[8]

Farming interests are concerned about barberry as a host plant for rust. ”Black stem rust is one of the most destructive plant diseases that is known to exist in the United States. The disease is caused by a fungus that reduces the quality of and yield of infected wheat, oat, barley, and rye crops by robbing host plants of food and water. In addition to infecting small grains, the fungus lives on a variety of alternate host plants that are species of the genera Berberis, Mahoberberis, and Mahonia. The fungus is spread from host to host by windborne spores.”[9]

A common sentiment is expressed in the following web log from Pugent Sound: “In some parts of the country Barbarries(sic) have become invasive but this hybrid (Berberis thunbergii 'Aurea') doesn't really set any seed and my clump of 3 plants has only reached two feet high and four feet across. Not bad for almost 5 years in the ground. It's a wonderful plant that really requires no special care. Certainly a keeper.”[10] As I have noted before in my postings, Monday, January 15, 2007; Invasive: thoughts and threads, it is quite possible that the plants in the garden do not produce many seeds, however, the possibility of cross pollination with species already “naturalized” is not addressed.

There is work under way to find a truly sterile Japanese barberry. “Mark Brand, a professor of plant science, and Yi Li, an associate professor of plant science, are experimenting with two different approaches to developing a sterile form of the plant that would have its desirable features, without producing seeds.”[11]

I have included a sample of the genus Berberis which is by no means complete or exhaustive. I also have tried to find state or university citations of barberry as invasive species in a sample of eastern and mid western states. I would be appreciative of any additional information or links which I will add to this list and give credit to the submitting source. Any additional from states not listed would be included gladly. Any corrections are encouraged.

Species list citation except when otherwise foot noted[12]

Berberis aggregata C. K. Schneid. -- salmon barberry : China[13]
Berberis canadensis P. Mill. -- American barberry, Allegheny barberry: North America[14]
Berberis bergmanniae – Chinese barberry; China (Szechuan; Hupeh)[15]
Berberis buxifolia Lam. -- Magellan barberry; southern Chile, Argentina[16]
Berberis x chenaultii qv. Berberis x hybridogagnepainii 'Chenaultii' Ahrendt[17] -- ornamental only[18]
Berberis darwinii Hook. -- Darwin's barberry, Argentina; Chile (invasive)[19]
Berberis fendleri Gray -- Colorado barberry; Colorado, Itah, New Mexico[20]
Berberis (x) gladwynensis – William Penn barberry; A hybrid of B. verruculosa and B. gagnepainii [21]
Berberis harrisoniana Kearney & Peebles -- Harrison's barberry; Sonoran desert: southwestern Arizona[22]
Berberis haematocarpa -- Red Barberry, Desert Barberry; North America, Colorado,
New Mexico, Texas, Arizona, California , Nevada, Mexico - Sonora[23]
Berberis julianae Schneid. -- wintergreen barberry, Julian’s barberry; China - Guizhou, Hubei, Sichuan[24]
Berberis koreana Palib. -- Korea, South - Kyonggi[25]
Berberis ×mentorensis L. M. Ames -- Mentor barberry; ornamental only[26]
Berberis ×ottawensis Schneid.; ornamental only[27]
Berberis sargentiana C. K. Snied. -- Sargent's barberry; China[28]
Berberis ×stenophylla Lindl. = Berberis darwinii × B. empetrifolia; ornamental only[29]
Berberis thunbergii DC. -- Japanese barberry; Japan (invasive CT, MA)[30]
Berberis vulgaris L. -- common or European barberry; Western Asia: Turkey. Caucasus: Russian Federation; Austria; Belgium; Czechoslovakia; Germany; Hungary; Netherlands; Poland; Switzerland; Belarus; Ukraine [incl. Krym]; Albania; Bulgaria; Greece; Italy; Romania; Yugoslavia; France [incl. Corsica]; Spain[31] ;(invasive WI)[32]
Berberis wilcoxii Kearney -- Wilcox's barberry; North America: New Mexico, Arizona,
Northern Mexico: Mexico - Sonora[33]
Berberis verruculosa Hemsl. & E. H. Wilson – Warty barberry ; China - Sichuan[34]
Berberis wisleyensis Ahrendt, misapplied to B. wisleyensis in cultivation -- Wisley barberry;

Exotic Pest Plant Councils as well as native plant societies refer to invasive barberry at great length, including SE-EPPC and MA-EPPC among many.

Maine: University of Maine Cooperative Extension Bulletin #2504
Vermont: many sites and references from out of state; no state site found as of this writing
New Hampshire: NH Dept. of Agriculture Markets & Food Plant Industry DivisionIndustry Division
Connecticut: Connecticut Botanical Society; Univ. Conn.
Massachusetts:Massachusetts Prohibited Plant List
Rhode Island: Rhode Island Invasive Species Council
New York: Invasive Plant Council of NYS
Pennsylvania: The Pennsylvania Bureau of Forestry and USDA Forest Service
New Jersey: Appendix to Policy Directive 2004-02
Invasive Nonindigenous Plant Species
Delaware: Delaware Natural Heritage Program
Maryland: Maryland Invasive Species Council,” Species of Concern”
Virginia: Invasive Alien Plant Species of Virginia
West Virginia: many sites and references from out of state; not listed on Invasive Species site
North Carolina: many sites and references from out of state; no state site found as of this writing
South Carolina: many sites and references from out of state; no state site found as of this writing
Ohio: does not appear on top ten list from Ohio Department of Natural Resources
Indiana: does not appear in list from Invasive Plants in Indiana
Michigan: many sites and references from out of state; not listed on Invasive Species site
Illinois: does not appear in list from Illinois Department of Natural Resources
Wisconsin: Wisconsin Manual of Control Recommendations:
Ecologically Invasive Plants
Minnesota: Minnesota Department of Natural Resources
Kentucky: does not appear in list from Kentucky Division of Forestry
Tennessee: many sites and references from out of state; no state site found as of this writing
********************************************************************************
[1] http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/shrubs/cultivars/berberis_thunbergii-table.html
[2] Invasive Plants of the Eastern United States (John Randall ); http://www.invasive.org/eastern/midatlantic/beth.html
[3] Invasive Plants of the Eastern United States (John Randall ); http://www.invasive.org/eastern/midatlantic/beth.html
[4] Plant Conservation Alliance, Alien Plant Working Group; http://www.nps.gov/plants/alien/fact/beth1.htm
[5] http://www.google.com/url?sa=X&start=0&oi=define&ei=4QS-RvOsJoeier6TrPAK&sig2=NZ5rpEJXv8g6WRwCzMwPjQ&q=http://www.cactus-art.biz/note-book/Dictionary/Dictionary.htm&usg=AFQjCNEt3hKUmxly-2G9U8gD0ci4ilnUbg
[6] http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/shrubs/cultivars/berberis_thunber-var-table.html
[7] http://www.hort.uconn.edu/plants/b/berthu/berthu1.html
[8] Twombly Nursery
[9] Federal Register: 5777; Vol. 71, No. 23; Friday, February 3, 2006
[10] BobsGarden.com
[11] Researchers Outsmarting Popular But Invasive Barberry Shrub;By Beth Krane
[12] USDA NRCS; http://plants.usda.gov/java/ClassificationServlet?source=display&classid=BERBE
[13] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6806
[14] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6826
[15] © 1998-99 Philippe Faucon, All Rights Reserved
[16] http://oregonstate.edu/dept/ldplants/bebun-i.htm
[17] Natural Resources Canada; http://www.nrcan-rncan.gc.ca/
[18] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6831
[19] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6845
[20] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?411282
[21] http://oregonstate.edu/dept/ldplants/beglwp.htm
[22] © 1998-2005 Philippe Faucon; All Rights Reserved.
[23] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?413268
[24] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6892
[25] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6896
[26] States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?105012
[27] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6929
[28] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6955
[29] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6967
[30] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6974
[31] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?6992
[32] USDA NRCS; http://plants.usda.gov/java/profile?symbol=BEVU
[33] United States Department of Agriculture Agricultural Research Service, Beltsville Area; http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?413269
[34] United States Department of Agriculture Agricultural Research Service, Beltsville Area;; http://www.desert-tropicals.com/Plants/Berberidaceae/Berberis.html