Buckthorn
is a small, shrubby tree. Its poisonous, small, black berries are often
mistaken for wild black cherries. This non-native plant has become a weedy
nuisance in woodlands and fence rows, competing with more desirable native
trees and shrubs. Planting of buckthorn is no longer permitted.
In 1999, the Minnesota
Department of Agriculture declared European or common buckthorn and glossy
buckthorn restricted noxious weeds. This means that sale, transportation,
or movement of this plant is prohibited statewide by the Minnesota
Department of Agriculture. Both species are considered invasive because
they are capable of rapidly spreading and replacing native species
throughout Minnesota.
In the past, Common
Buckthorn was more widely planted for formal hedges. It is now more
commonly encountered as a wild plant. Birds spread the seeds after eating
the often abundant fruits. If you see seedlings coming up, remove them
promptly.
Buckthorn twigs are
tipped with a short, sharp thorn. The buds are slightly curved and pressed
to the stem. The leaves are dark green with curved main veins, and hang on
late into the fall without changing color. This is the easiest way to
identify buckthorn. The berries are black and contain several seeds. The
juice is greenish-black.
European buckthorn is the
most problematic species of buckthorn because it is both drought and shade
tolerant. These characteristics enable it to become invasive in woodland
understories or at the edges of prairies or fields. In more recent years,
glossy buckthorn has also been shown to be an invasive plant, problematic
mainly in wetlands and moist woodlands. Both types of buckthorn have berry
clusters that attract birds who then deposit the seeds in their droppings.
This process allows for large quantities of buckthorn to become distributed
over vast and diverse areas.
Physical
Removal of Buckthorn
Intensive vegetation
clearing is prohibited within 75’ of Lake Minnetonka, so lakeshore property
owners should contact the City before beginning lakeshore vegetation
clearing activities.
For buckthorn stands
containing individual plants 3/8 inch in diameter or less, hand pulling may
be the most effective method of removal. Uprooting the small plants can be
aided by using a weed wrench or shovel to help loosen their roots. This is
a practical method for small stands of buckthorn, but may not be practical
for large stands due to the amount of labor involved. Buckthorn plants that
are greater than 3/8 inch in diameter may be more difficult to pull out of
the ground. To loosen their roots, soak the soil around the trunk for
several days before pulling. Before you pull or dig buckthorn out of your
soil, call Gopher State One to ensure there are no buried utilities in the
area.
Stump
Treatment
When controlling large
quantities of buckthorn, cutting the stems, then painting or spraying the
stumps with the herbicide glyphosate (commonly sold as RoundUp) is quite
effective. You will need to buy a concentrated form containing 25 percent
or higher amounts of the active ingredient, glyphosate. Stores may carry
concentrated forms containing smaller percentages, so it is important to
read the fine print on the label. Farm and landscape supply stores often
sell this more highly concentrated glyphosate.
The proper time to cut
buckthorn and apply glyphosate is when the plant is active or when the
leaves are fully expanded and temperatures are above 32o F.
This will ensure that the herbicide is taken up by the plant. The
herbicide must be applied within 24 hours of cutting, but applying it
immediately after cutting is best. In cases where more than a few
plants are treated, it is beneficial to add a dye to the herbicide to mark
cut stumps and bark you’ve already sprayed. Laundry blueing works well, is inexpensive, and is
available at the grocery store. If you choose to use an herbicide as a
means of buckthorn control, always read and follow label direction to
prevent danger to yourself (the applicator), and to the environment, and to
ensure that the herbicide will work effectively.
Frequent
Pruning
When feasible, removal of
buckthorn in the landscape is encouraged. When it is not feasible to remove
buckthorn, such as the case for some homeowners with large mature hedges,
one last option may be used to prevent the spread of buckthorn without
removing the plants. Pruning or shearing frequently (at intervals of every
3-4 weeks) can dramatically reduce or eliminate the flowers and subsequent
berries. This method is effective in preventing birds from eating the
berries and distributing buckthorn seeds only if it is done
frequently as suggested above.
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