The Yellowstone Arboretum has partnered with the Platinum Project and West High School student Hunter Gibbs to begin a European Buckthorn removal program. The European Buckthorn is an invasive species that has populated areas in and around Billings. The purpose of this project is to introduce a physical and natural approach to eradication. Because the arboretum is on the grounds of ZooMontana no chemicals will be used for this project. We hope the exposure of this problem, to visitors, will help in the education of it's removal importance. The City of Billings has been eradicating Buckthorn in Riverfront Park and under their guidance Hunter Biggs will be working in two areas of the arboretum located near the Wolverine and Wolf habitats.. Here's some more information that may be of interest to you:

" Hello, my name is Hunter Gibbs, and I'm a rising senior from Billings West High School in Billings, Montana. For my senior project, titled Project Buckthorn, I am working to spread awareness on buckthorn, an invasive species in Montana, by removing an outbreak at the Yellowstone Arboretum @ZooMontana "

I just created a GoFundMe page. Please help me fundraise as a team member. View and join the fundraiser here: https://gofundme.com/f/project-buckthorn

Meet the Hunter


Rhamnus cathartica is a deciduous shrub or small tree that can grow to 25 ft. (7.6 m) in height. The bark is dark gray and the inner bark is orange (easily seen when the tree is cut). Twigs are usually tipped with a sharp spine.


The leaf arrangement is usually sub-opposite, but examples of opposite and/or alternate arrangements are commonly found. Leaves are dark green, oval, 1.5-3 in. (3.8-7.6 cm) long, slightly serrate with 3 to 4 pairs of curving veins and a somewhat folded tip.


Flowering occurs in the spring, with fragrant, yellow-green, 4-petaled flowers developing in clusters of 2 to 6 near the base of the petioles. Plants are dioecious (male and female flowers occur on separate plants).


Appearing in the fall, the small, purple to black fruit are 0.25 in. (0.6 cm) in diameter. The fruit contains 3-4 seeds. Birds and other wildlife eat the fruit and disperse the seeds.

Ecological Threat

Rhamnus cathartica invades forests, prairies, and savannas in the Midwestern United States and can form dense thickets crowding out native shrubs and understory plants. It is difficult to remove and can regenerate after cutting or burning. It is a native of Europe and was introduced into the United States as an ornamental shrub.


Buckthorn removal tip #1.  

If you cut down a buckthorn plant be sure to kill the plant by applying an herbicide to the freshly cut stump. If you don’t treat the stump it will grow back almost immediately with 3 – 8 sprouts of growth making the problem 3 – 8 times worse. Don’t cut down buckthorn unless you plan to treat it with an herbicide.

Buckthorn removal tip #2.  

If you only have the time to cut down a few plants in and around your yard focus on the female plants. They have the berries which contain the berries/seeds. If you cut down 5-10 female plants each year in your area you will make a huge in slowing the spread of buckthorn.

Buckthorn removal tip #3.  

Cut-Stump Method. The most popular herbicide used to kill buckthorn is Round Up Plus Concentrate. Make sure that the herbicide you purchase is at least 18% – 20% glyphosate. Use it undiluted. If you find glyphosate at 40% strength use a 50 – 50 mix of water and herbicide. Use a paint brush to apply to the herbicide to freshly cut buckthorn. This will kill the plant.

Buckthorn removal tip #4.  

The best time of the year to use the cut-stump method is late July through February. During this time of the year the sap is flowing back down in to the root zone. You can still use the cut stump method from March through Mid-July. During this time the sap is flowing outward towards the branches and you will not have as high of a kill rate.

Buckthorn removal tip #5.  

Use a large pliers to pull smaller buckthorn out of the ground. (8” – 30” plants) This is easier to do when the ground is wet. Pulling the small plants out during this stage of growth is a lot easier than removing larger plants.

Buckthorn removal tip #6.  

The best time to kill buckthorn with a foliar herbicide is during the late summer and fall months. The plants are slightly stressed and the sap is flowing back towards the roots. Use recommended application rates found on the side of any vegetation killer herbicide. Make sure you are careful to keep the herbicide off of the native plants in the area. Do it on a calm day with no wind.

Buckthorn removal tip #7.  

After you remove the established growth it is important to kill any new growth on a yearly basis. Buckthorn seeds are viable in the ground for up to 5 years. After a few years the amount of new growth will decrease on a yearly basis until there are no more seeds left to germinate.

Buckthorn removal tip #8.  

If you have a large area infested with buckthorn don’t be overwhelmed. Set realistic yearly goals. Try to remove buckthorn 10 – 20 feet at a time. Start by any existing trail and work your way out. Go back year after year and continue to make new progress.

Buckthorn removal tip #9.  

If you are removing buckthorn on private property you should consider burning the cut buckthorn. Buckthorn easily burns within 6 – 8 weeks after being cut.

Buckthorn removal tip #10.  

If you don’t have any herbicide to kill the buck you can cover the cut stumps with a thick plastic. You’ll need to weigh down the plastic with something like rocks. You can also use old soup cans to cover cut stumps. The stump needs to be cut close to the ground so the soup can is buried in the ground at least 1 inch.

Removal Process