Common Name: Common buckhorn (European buckthorn, Hart's thorn, European waythorn, Rhineberry)Author: Colleen Alderson
Scientific Name: Rhamnus cathartica L.
Identification: A shrub or small tree that can grow to 22 feet and a trunk expanse of 10 inches. The leaves are wide, oval-shaped with 3 to 4 pairs of upcurved veins. Leaves remain green late into fall. In spring clusters of 4 petaled flowers grow from stems and are yellow-green. Round small black fruits form in the fall. Two native American buckthorns grow in the northeast and are similar in appearance. Carolina buckthorn (Phamnus caroliniana) is usually shorter growing 10 to 15 feet tall and has 8 to 10 pairs of veins. The Alder buckthorn is even smaller, growing to 3 feet and has leaves with 6 to 7 pairs of veins.
Original Distribution: The Common buckthorn is a native plant throughout Europe, temperate areas of Asia, and northern Africa.
Current Distribution: The Plants Database for the U.S. Department of Agriculture reports that the Common buckthorn is found extensively in the continental United States. The plant is found in every continental state, except for Washington, Oregon, Nevada, New Mexico, Arizona, Texas, Tennessee, Louisiana, Oklahoma, Arkansas, Mississippi, Alabama, Georgia, and South Carolina. The Nature Conservancy also reports that the plant is also found extensively in Canada, from Novia Scotia to Saskatchewan.
Site and Date of Introduction: Most references searched on the web cite the introduction of the plant to be in the 1800s. The only specific year reference is on Wisconsin's Department of Natural Resources website which states that the plant was planted as hedgerows as early as 1848.
Mode(s) of Introduction: The Common buckthorn was originally planted as an ornamental shrub and for wildlife habitat. The plant has spread from its introduction as shrubs to other areas because birds and mice eat the fruit, which produces three to four seeds. Additionally, the fruit creates a laxative effect making the plant easily spread by birds distributing its seeds. .
Reason(s) Why it has Become Established: The plant was introduced because of its hardiness as an ornamental plant. It is able to survive in a variety of soil and light conditions. The plant can grow in sandy, loamy, or heavy soils, and can grow in very alkaline soil. It can grow in partial shade or areas with no shade. Woodlands, savanannas, and prairies provide conditions for the plant to survive and thrive. The plant is dense and crowds out native plants and herbaceous plants. The density of plants occurs because there are a large number of fruits that are produced by a female. Its broad leaves prevent sunlight from reaching low-lying plants. The plant has a long growing season with leaves growing early compared with other woodland plants and remain late into the fall with its fruit. Seeds are hearty and are able to remain in soil for years even after a plant has been removed.
Ecological Role: Common buckthorn serves as a food source for birds and small animals that reside in prairies and woodlands. The plant is very hardy and is resistant to cattle grazing. Rabbits can damage young plants, so woodlands are kept in check in the early spring to some extent, perhaps allowing for other herbaceous plants to grow.
Benefit(s): The plant was used ornamentally due to the hardiness of the plant and for the length of time that the plant remains with its green leaves. The dried berries and dried bark are used medicinally for constipation. The berries provide a food source for birds. The tall shrubs also provide nesting for birds, such as wood thrushes. Yellow dye for color paper and maps is made from the bark of the plant. Green, yellow, orange, and brownish dyes for watercolor painting are made from the immature fruit by mixing it with gum arabic and limewater.
Threat(s): The plants' principle threat is to crowd out other shrubs and herbaceous plants through its rampant dispersal of seeds and elimination of sunlight to the understory. Common buckthorn invades oak forests, savannas, prairies and riparian woods and eliminates native plant diversity in the understory. Fire adapted ecosystems such as prairies and savannas do not experience fire cycles due to the lack of understory that the Common buckthorn has overtaken. The Common buckthorn is also an overwintering host to the soybean aphid, an agriculture pest resulting in plant stunting and crop loss. Increased nest predation of such birds as the American Robin and Wood thrush may occur due to the Common buckthorn. The causes are due to lower nest heights, the lack of thorns in the plants which prevent mammals from intruding, and ude to the pants thick and sturdy branches which aid the stability of llarger mammals trying to disturb a nest.
Control Level Diagnosis: The Common buckthorn should be controlled and a medium level priority control diagnosis is assigned. The plant is extremely invasive and should be removed once it is detected in field edges and forest borders.
Control Method: Early recognition and removal from field edges, forest borders is the first way to control the invasive plant to prevent its intrusion into the larger ecosystem. Both mechanical and chemical control methods are used to eradicate the plant. Mechanical methods include controlled fires, or digging and pulling the plant and chopping the stump of the shrub with an ax or chainsaw. Removal of plants before seedlings occur is best. Fire is more succesful in smaller plant groupings, while numerous controlled burns may be required with larger density areas to remove the seed bank. Chemicals are used in conjunction with plant and stump removal where fires are prohibited. Application is done in the fall when the leaves are still readily visible and most other plants are dormant. Application should be right after stump removal. Chemical application to the basal bark in the dormant season can also be done. General use herbicides include glyphosate or triclopyr. Reapplication of sprouts is also required. Active management of invaded areas is important because seeds can remain in the soil for up to five years. The planting of native plants in an area previously invaded by the Common buckthorn should also be planted with native plants of the appropriate ecosystem. The U.S. Department of Agriculture also states that a biocontrol method, insects, has been researched in Europe and release of the insects in the United States may take place sometime between 2007 and 2010.
U.S. Department of Agriculture, Germplasm Resources Information Network, http://www.ars-grin.gov
U.S. Department of Agriculture, Natural Resources Conservation Service PLANTS profile, http://plants.usda.gov/java/profile?symbol=RHCA3
U.S. Departmentof Agriculture, Forest Service, http://www.na.fs.fed.us/fhp/invasive_plants/weeds/common-buckthorn.pdf
Whelan, Christopher J., Exotic Shrubs and Songbird Nest Success, Illinois Natural History Survey Reports Summer 2000. http://inhs.uiuc.edu/inhsreports/sum_2000/exotic.html
Wisconsin Department of Natural Resources, http://www.dnr.state.wi.us/invasives/fact/buckthorn_com.htm
John M. Randall of The Nature Conservancy posted by the National Park Service, http://www.nps.gov/plants/alien/fact/rhca1.htm