Common buckthorn is a shrub
or small tree that can grow to 22 feet in height and have a trunk up to 10
inches wide. The crown shape of mature plants is spreading and irregular.
The bark is gray to brown, rough textured when mature and may be confused
with that of plum trees in the genus Prunus. When cut, the inner bark is
yellow and the heartwood, pink to orange. Twigs are often tipped with a spine.
In spring, dense clusters of 2 to 6, yellow-green, 4-petaled flowers emerge
from stems near the bases of leaf stalks. Male and female flowers are borne
on separate plants. Small black fruits about 1/4 inch in cross-section and
containing 3-4 seeds, form in the fall. Leaves are broadly oval, rounded
or pointed at the tip, with 3-4 pairs of upcurved veins, and have jagged,
toothed margins. The upper and lower leaf surfaces are without hairs. Leaves
appear dark, glossy green on the upper surface and stay green late into fall,
after most other deciduous leaves have fallen.
A similar problem exotic species is Rhamnus
frangula, glossy buckthorn. Glossy buckthorn does not have a spine
at twig tips, leaves are not toothed, and the undersides of the leaves
NOTE: Several native
American buckthorns that occur in the eastern U.S. that could be confused
with the exotic species. If in doubt, consult with a knowledgeable botanist
to get an accurate identification. Carolina buckthorn (Rhamnus
caroliniana), is a lovely native shrub that has finely toothed
leaves somewhat resembling those of black cherry, and are smooth on the
underside; it produces attractive fruits from August to October. Alder
buckthorn (Rhamnus alnifolia), is a low-growing
shrub that may grow to a maximum of 3 feet in height, and has leaves
with 6-7 pairs of veins.
tend to form dense, even-aged thickets, crowding and shading out native shrubs
and herbs, often completely obliterating them. Dense buckthorn seedlings
prevent native tree and shrub regeneration. In fire-adapted ecosystems such
as savannas and prairies, the lack of vegetation under buckthorn prohibits
fires. Buckthorn control is also of interest to small grain producers; the
shrub is an alternate host of the crown rust of oats, which affects oat yield
IN THE UNITED STATES
Common buckthorn has become naturalized from
Nova Scotia to Saskatchewan, south to Missouri, and east to New England.
IN THE UNITED STATES
Common buckthorn prefers lightly shaded conditions.
An invader mainly of open oak woods, deadfall openings in woodlands, and
woods edges, it may also be found in prairies and open fields. It is tolerant
of many soil types, well drained sand, clay, poorly drained calcareous,
neutral or alkaline, wet or dry.
Common buckthorn was introduced
to North America as an ornamental shrub, for fence rows, and wildlife habitat.
Introduction of buckthorn was based on its hardiness and ability to thrive
in a variety of soil and light conditions.
BIOLOGY & SPREAD
is a dioecious plant, meaning that each plant produces only male or female
flowers and fruiting trees are always female. Most of the fruits fall directly
beneath the shrubs, creating a dense understory of seedlings characteristic
of common buckthorn stands. The plentiful fruit is eaten by birds and mice
and is known to produce a severe laxative effect, helping distribute seeds
through birds, often far from the parent plant. Buckthorn often establishes
beneath trees at the edges of forests and fields.
physical and chemical methods are available for control of common buckthorn
and glossy buckthorn (Rhamnus frangula), also an invasive exotic plant.
Prescribed fire is one method proposed for controlling buckthorn seedlings
in fire-adapted natural areas, from late March to early May, most recently
by Boudreau and Willson. In the upper Midwest conduct burns as soon as leaf
litter is dry; resprouts will be less vigorous due to low carbohydrate levels.
Burning every year or every other year in established stands may be required
for 5-6 years or more. Unfortunately, buckthorn seedings often grow in low
litter areas, unsuitable for frequent prescribed fire. In dense stands, seedlings
and saplings may be cut and dropped on site, creating fuel for future fires.
Buckthorn seedlings appear vulnerable to fire, perhaps due to their poorly
established root structure. Fire will top kill a mature plant, but resprouting
does occur. Uprooting of ½ inch diameter seedlings by hand or up to 1 1/2
inch diameter using a weed wrench is effective, but care should be taken
to avoid excessive disturbance to the soil, which can release buckthorn seeds
stored in the soil.
Careful application of herbicides
has been found to effectively control buckthorn in Illinois. The McHenry
Conservation District (MCICD) reports excellent results using a triclopyr
herbicide at the rate of 1:4 herbicide:water with dye on cut stumps during
the growing season, from late May to October. The product label suggests
avoiding treatment during the spring sap flow. To extend the work season,
the use of a triclopyr herbicide was also applied to cut stumps during winter
and was reported to be effective by MCICD and the Minnesota Region V State
Frill application (applying herbicide into the
cambial layer of fresh cuts on the tree trunk) using the 1:4 rate of triclopyr
herbicide with oil and dye was also effective. Experiments at the University
of Wisconsin Arboretum report good results using a mixture of 1 part triclopyr
herbicide to 7 parts oil on cut stumps, or a 1 part triclopyr herbicide to
16 parts oil mixture applied as a basal bark treatment to stems less than
3 inches across. For fall applications, the Minnesota Department of Natural
Resources, Region V State Parks Resource Management has used a 1 part glyphosate
herbicide to 5 parts water mixture applied immediately to cut stumps using
a hand sprayer. Initial checks indicated over 85 percent control at the test
USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
SUGGESTED ALTERNATIVE PLANTS
landscaping and wildlife plantings many native low trees and shrubs are available
from commercial nurseries. Examples include American elder (Sambucus canadensis),
Black chokeberry (Aronia melanocarpa), and Juneberry (Amelanchier
alnifolia). Please contact your local native plant society for recommendations
of plants native to your particular area.
Susan Wieseler, Minnesota Department of Natural
Resources, Rochester, MN
Jil M. Swearingen, National Park Service, Washington,
John M. Randall, The Nature Conservancy, Davis,
Archibold, O. W., D. Brooks, and L. Delanoy.
1997. An investigation of the invasive shrub European Buckthorn, Rhamnus
cathartica L., near Saskatoon, Saskatchewan. Canadian Field Naturalist
Boudreau, D., and G. Willson. 1992. Buckthorn
research and control at Pipestone National Monument (Minnesota). Restoration
and Management Notes 10:1 94-95.
Converse, C. 1985. Element Stewardship Abstract, Rhamnus
cathartica. The Nature Conservancy.
Glass, S. 1994. Experiment finds less herbicide
needed to control Buckthorn (Wisconsin). Restoration and Management Notes
Swearingen, J. 2009. WeedUS Database of Plants Invading Natural Areas in the United States: Common Buckthorn (Rhamnus cathartica). http://www.invasive.org/weedus/subject.html?sub=3070.
USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Plant Conservation Alliance, Alien Plant Working Group.