Barberry-Beauties Gone Bad
By Elizabeth Adlung, Master Gardener
Barberries are shrubs with graceful arching branches of summer foliage in lush green, gold, or red-so hardy they grow all over the world in good or bad soil, in sun or shade. They have delicate yellow flowers in summer and berries in fall and winter that birds adore. They are effective for crime prevention under windows vulnerable to burglars because they are so prickly and thorny. Deer find them unpalatable. Barberries seem like a landscaper’s dream. Why are they considered a “Least Wanted Plant” by the Plant Conservation Alliance(PCA)? We have a long and problematic history with them.
Our History with Barberries
The barberry (Berberis) family is huge with about 450-500 species native to the temperate and subtropical regions of Europe, Asia, Africa, North America, and South America. Only one species – the American barberry (Berberis canadensis)- is native to North America.
Our problems with barberries really began when early settlers brought the common or European barberry (Berberis vulgaris) to North America and used it for hedgerows, dye, and jam. Both American and European species are an intermediate host for Puccinia graminis (black rust), a rust disease of wheat. Wheat farmers accused barberries of spreading rust as early as 1660, but they were derided as superstitious by the jam makers. The matter was not settled scientifically until 1865. Because of the impact of this disease on wheat crops, cultivation of European and American barberry is prohibited in many areas.
Japanese barberry seeds (Berberis thunbergii) were sent from Russia to the Arnold Arboretum in Boston, Massachusetts in 1875 and introduced to the U.S. and New England as an ornamental plant. In 1896, barberry shrubs grown from these seeds were planted at the New York Botanical Garden. Japanese barberry was later promoted as a substitute for common barberry (Berberis vulgaris). In the next hundred years, many attractive variations or cultivars of the original Japanese barberry have been developed – ‘Crimson Pygmy,’ ‘Aurea,’ ‘Sparkle,’ and many others, which sell briskly in garden centers. Now we have problems!
Barberry Threatens Native Habitats
Japanese barberry has escaped from cultivation and is progressively invading natural areas. At this time. it is reported to be invasive in at least twenty states. It is a particular threat to open and second-growth forests. An established colony can eventually grow thick enough to crowd out native understory plants. Birds eat the red berries and spread the shrub into new areas.
Now we find Japanese barberry in old fields, open woods, floodplains, along power lines, and on roadsides. The plants are both sun- and shade-tolerant and grow successfully in a variety of soil types as far north as Nova Scotia, south to North Carolina, and west to Montana. Once established, barberry displaces native plants and reduces wildlife habitat and forage. White-tailed deer avoid barberry and prefer to feed on native plants, which gives barberry a competitive advantage.
Management Options
Do not plant Japanese barberry. Because it is a prolific seed-producer with a high germination rate, prevention of seed production should be a management priority. Because barberry can sprout again from root fragments remaining in soil, thorough removal of root portions is important. Manual control works well but may need to be combined with chemicals in large or persistent infestations. No biological control organisms are available for this plant.
- Chemical:Â Treatments using the systemic herbicides glyphosate (e.g., Roundup(r)) and triclopyr (e.g., Garlon) have been effective in managing Japanese barberry infestations that are too large for hand pulling. For whole plant treatment, apply a 2% solution of glyphosate mixed with water and a surfactant. This non-selective herbicide should be used with care to avoid impacting non-target native plants. Application early in the season before native vegetation has matured may minimize non-target impacts. However, application in late summer during fruiting may be most effective. Triclopyr or glyphosphate may be used on cut stumps or as a basal bark application in a 25% solution with water, covering the outer 20% of the stump.
- Manual:Â Because Japanese barberry leafs out early, it is easy to identify and begin removal efforts in early spring. Small plants can be pulled by hand, using thick gloves to avoid injury from the spines. The root system is shallow, making it easy to pull plants from the ground, and it is important to get the entire root system. The key is to pull when the soil is damp and loose. Young plants can be dug up individually using a hoe or shovel. Hand pulling and using a shovel to remove plants up to about 3 feet high is effective if the root system is loosened up around the primary tap root first before digging out the whole plant.
- Mechanical:Â Mechanical removal using a hoe or Weed Wrench(r) can be very effective and may pose the least threat to non-target species and the general environment at the site. Tools like the Weed Wrench(r) are helpful for uprooting larger or older shrubs. Shrubs can also be mowed or cut repeatedly. If time does not allow for complete removal of barberry plants at a site, mowing or cutting in late summer prior to seed production is advisable.
Native Alternatives For Your Landscape
Many attractive native shrubs are available that make great substitutes for Japanese barberry. A few examples include bayberry (Myrica pensylvanica), inkberry (llex glabra), winterberry (llex verticillata), arrow-wood (Viburnum dentatum), mountain laurel (Kalmia latifolia), ninebark (Physocarpus opulifolius), hearts-a-bustin’ (Euonymus americana), New-Jersey tea (Ceanothus americanus), wild hydrangea (Hydrangea arborescens), silky dogwood (Cornus racemosa), red chokeberry (Aronia arbutifolia), and black chokeberry (Aronia melanocarpa).
References
Many sources of information are available on topics mentioned in this article. A few are listed below:
http://www.nps.gov/plants/ – Plant Conservation Alliance (PCA) website.
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.
Swearingen, J. 2004. WeedUS: Database of Invasive Plants of Natural Areas in the U.S. (in progress) http://www.nps.gov/plants/alien
USDA Plants Database. http://plants.usda.gov/
Delaware River Invasive Plant Partnership, Invasive Plant Fact Sheets, http://www.paflora.org/DRIPP.html
Invasive Plant Atlas of New England, http://invasives.eeb.uconn.edu/ipane/
National Invasive Species Information Center, http://www.invasivespeciesinfo.gov
The Nature Conservancy Invasive Species Initiative, http://tncweeds.ucdavis.edu/esadocs.html
Brunelle, H. and B. Lapin. 1996. Invasive Plant Information Sheet: Japanese Barberry. Middletown, CT: The Nature Conservancy of Connecticut.
SOURCE: Information on the barberry species is taken, in part, from the Plant Conservation Alliance, Alien Plant Working Group, Weeds Gone Wild website (http://www.nps.gov/plants/alien/factmain.htm) and the Invasive Plant Association of New England Fact Sheets (http://invasives.eeb.uconn.edu/ipane/index.htm).
Pike County Master Gardeners are available every Tuesday from 10 a.m. until noon to answer general gardening questions, by phone, 570-296-3400, or in person at the Penn State Extension Office, 514 Broad Street, Milford.
What is a Native Species?
All organisms are native to planet Earth (until further notice), and each species of bacteria, fungi, plant, animal, and other creatures has a home somewhere on this planet where it has existed and evolved for thousands of years. A native or indigenous species is one that occurs in a particular place without the help of humans, which is not always easy to determine. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.
An organism’s home, or native range, is determined by a host of influences such as climate, geology, soils, hydrology, biological interactions, and natural dispersal. Living things disperse within their native ranges by moving around on their own or with the help of air, water, wind, and other animals. However, beginning with Columbus’ discovery of America in the 15th century, people have played an increasingly significant role in moving plants, animals, and other organisms around the world, to places far beyond their likely natural dispersal ranges, and this is where the trouble lies.
–from Alien Plant Working Group http://www.nps.gov/plants/alien
What Makes an Exotic Species Invasive? (When is a Guest a Pest?)
Many non-native species exist in apparent harmony in environments where they were introduced. For example, a relatively small number of exotic plants (e.g., corn, wheat, rice, oats) form the basis of our agricultural industry and pose little to no known threat to our natural ecosystems. The most important aspect of an alien plant is how it responds to a new environment. An invasive species is one that displays rapid growth and spread, establishes over large areas, and persists. Invasiveness is characterized by robust vegetative growth, high reproductive rate, abundant seed production, high seed germination rate, and longevity. Some native plants exhibit invasive tendencies in certain situations.
–from Alien Plant Working Group http://www.nps.gov/plants/alien
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