P.O. Box 5274
Madison, WI 53705-0274
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European buckthorn is a troublesome exotic invasive that spreads readily
through woods and savannas. It is a major threat to Wisconsins ecosystems.
Click on images for a larger view.
Invasion of a pine forest by buckthorn.
Such a dense cover reduces light to the forest floor, effectively eliminating native understory vegetation.
Common buckthorn (Rhamnus cathartica) and its relative glossy
buckthorn (Rhamnus frangula) are serious invaders of Wisconsins
wooded areas. They also commonly invade hedge rows of open fields, from
which they may gradually spread throughout a whole field. Both common
and glossy buckthorn are small trees or shrubs that can reach a height
of 20-25 feet. Buckthorn most often grows as a shrub, where it may send
out several shoots.
Characteristic orange inner bark of buckthorn.
Scratching the surface is a good way of ensuring that
one has a buckthorn plant.
Buckthorn has separate male and female plants; the latter are often easy
to recognize because they produce copious amounts of deep purple berries.
It is especially important to remove the berry-producing plants, because
they will otherwise be a constant source of infection for the area.
Buckthorn is of Eurasian origin and was introduced in North America as
an ornamental. It was planted for hedge rows in Wisconsin as early as
1849. Despite its insidious nature, it is still legally sold in the state
as an ornamental. It has become naturalized and has spread over most of
the southern and eastern parts of the state. Buckthorn is an especially
troublesome invader of natural oak savanna and oak woodland areas of southwestern
Leaves and fruit of common buckthorn, Rhamnus
Many bird species relish buckthorn berries. However, the berries contain
a chemical which acts as a laxative (hence the species name cathartica).
The defecation by the birds insures the spread of the seeds through the
habitat. Since female trees may produce abundant fruit, within a few years
there can be thousands of buckthorn seedlings in the area of a mature
tree. Buckthorn seeds are able to remain alive in the soil for years,
and new seedlings will continue to appear for years after the plants have
been removed from an area.
Early identification, before seed production has started, is vital.
Small buckthorn seedlings can be readily removed by hand, or with the
use of a weed wrench. Although effective, mechanical removal
disturbs the soil and encourages reinfestation or colonization of other
weeds so that loose soil should be tamped down to make a firm surface.
Controlled burns will usually top-kill seedings or small buckthorn trees,
but does not eradicate them. In order to control buckthorn by controlled
burning, it is essential that fire be continued annually until native
(fire-resistant) vegetation has become established. Use of fire is best
reserved for fire-dependent ecosystems such as prairies or oak savannas.
There are several herbicides that are very effective in control of buckthorn.
One of the most effective is triclopyr (Garlon; Dow Agrochemical). When
using an herbicide, it is essential that the label on the package be read
completely before use.
An effective way to control buckthorn is by the use of basal bark treatment
with Garlon in oil. Treatment is best done in the late fall or winter
when native vegetation has died back and will not be affected. Because
buckthorn plants retain their leaves long after native vegetation has
lost its leaves, they are readily recognized in the late fall. A concentration
of 12-15% triclopyr (active ingredient) in diesel fuel or kerosene is
recommended by the manufacturer. Use the herbicide in a backpack sprayer
with a nozzle that produces a solid cone or flat fan spray. Spray the
lower part of the trunk in such a manner that it becomes thoroughly wet,
including the root collar, but not to the point of runoff. Each stem of
the plant must be treated. Properly done, this basal bark treatment is
extremely effective and the plant will not leaf out the following growing
season. Once dead, the plant can be cut and removed, or allowed to stand
Another very effective way of eradicating buckthorn is to cut the plant
just above the ground level and treat the cut stump with triclopyr.
The same concentration of triclopyr should be used as for basal bark
treatment, but only the cut stump should be treated. It is useful to include
a blue or red dye in the herbicide mixture so that the cut stump treatment
can be monitored. A backpack sprayer or spray bottle can be used. Be sure
that the stump is thoroughly wetted with herbicide. This procedure is
economical of herbicide and confines the chemical to the stump itself,
but is more labor-intensive than basal bark treatment. However, it has
the advantage that the buckthorn plants themselves are being removed from
Although the cut stump procedure can be used at any time of the year,
the fall or winter is preferable because nontarget plants are not affected.
Also, this procedure is effective with plants of any size, even large
ones. Place all the cut material in a pile for subsequent burning.
Bark treatment is best in large infected areas, whereas cutting and treating
the cut stumps is best in relatively small areas, or in areas of high
Glove of Death technique (pdf)
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