Buckthorn management is one of the toughest challenges facing urban foresters. Buckthorn is an extremely invasive tree that has been displacing urban forests and wetlands for years. Unfortunately, there is no quick fix for our buckthorn dilemma. Buckthorn management is a long term and often costly endeavor. Management plans need to be in place on all levels with homeowners, municipalities, and urban foresters working together to halt the buckthorn invasion.
A Brief History of Buckthorn
Leaves of the common buckthorn.
Common buckthorn was commonly planted for years as a hedge or windbreak. The growth form is a multi-stemmed, medium sized tree. Female trees produce large quantities of fruit contributing to the rapid spread of buckthorn. Glossy buckthorn, or columnar buckthorn, has also been planted for years. Glossy buckthorn produces fruits continuously for several months, a common trait of invasive plants. Common buckthorn is generally associated with terrestrial plant communities, while glossy buckthorn is associated with wetland communities. However, they are readily seen invading uplands and lowlands together.
What’s wrong with buckthorn?
Common buckthorn was added to the “Restricted Noxious Weed List” in 1999 and can no longer be sold. Glossy buckthorn was added to the list in 2001. There are several attributes of buckthorn that put it on the top of the invasive plant list.
Cluster of fruit on a common buckthorn.
- Out competes native plants for light, space and nutrients
- Buckthorn fruit is readily spread by birds
- Seeds may persist in the soil for up to 6 years before germinating
- Leafs out early in spring and stays green in fall longer than other trees and shrubs
- Its thorns are dangerous and can injure persons in woodlands, parks, and other areas
- Has chemicals in its roots, leaves and fruit that inhibit the growth of other plants
- Are vigorous trees that are difficult to kill even with herbicides
- Creates a monoculture as it invades an area decreasing diversity of plant communities
Key Elements of a Buckthorn Management Program
When deciding how to design and implement a buckthorn management program, there are several factors that must be considered. These factors include budget, length of time that the buckhorn has been present, size and density of the buckthorn, season of the year, and size of workforce (or number of volunteers).
(1) The first phase of any buckthorn project would be to remove the medium and large buckthorn trees. Also, the stumps must be ground out or treated chemically to minimize re-growth. When dealing with a limited budget, remove the largest seed-bearing trees. This phase can be started whenever, but we feel optimum results can be achieved in the fall.
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Picture showing a thick understory of common buckthorn remaining green late into fall.
(2) The second step will be to pull or spray smaller seedlings. The choice between pulling or spraying will depend on the size of the management area, the number of seedlings in the area, and if using chemicals is the right choice for you. Some people would prefer not to use chemicals, but in larger areas it is often the most effective choice.
(3) Once the buckthorn is removed, there will be a flush of new growth from germinating seeds that have been lying dormant in the soil. This is caused by an increase in light penetration to the soil. During this phase, new seedlings need to be sprayed or pulled. This phase could last several years.
An understory of oak and elm with a high quantity of buckthorn seedlings that germinated once the large buckthorn trees were removed.
(4) The fourth phase of management will vary depending on how severe the buckthorn has displaced the native plants in the area. In some plant communities native plants will re-establish in time. However, in many areas, the buckthorn will have displaced native plants for so long, replanting will be necessary. This is a very important part of the restoration process. Unless native plants can re-establish, it will be easier for buckthorn to reinvade. Here are a few native plants that can be used in the replanting phase of buckthorn management.