By Sophia Cameron, Invasive Plant Management Intern and Jesse Wheeler, Vegetation Program Manager
Glossy buckthorn (Rhamnus frangula L.), is an invasive shrub species that has taken over the understories of many North American forests and wetlands. This prolific shrub has invaded several of Acadia’s diverse bogs, swamps, and forests. It is shade tolerant, allowing the shrub to establish successfully in densely forested areas. It can grow up to 20 feet tall but begins as multiple stems before developing a trunk at maturity. These early stems are greenish in color, and the older bark is grayish-brown and textured. Their leaves are simple, shiny, and untoothed. They are alternate but may appear opposite at first glance. The flowers are very small, and sometimes easy to miss. They have five white petals and bloom throughout the summer months. Their fruit grows in bundles of three to four fleshy berries and go from green to red to dark purple as they ripen through the summer.
Glossy buckthorn is frequently confused with its relative, common buckthorn (Rhamus cathartica). Though they appear very similar, they can be told apart based on the teeth that appear on the leaves of the common buckthorn, as well as having flowers with four petals instead of five. Common buckthorn is also invasive, but less so than glossy buckthorn in the Acadia region. Despite its name, glossy buckthorn stems are thornless, while common buckthorn has small spines on the end of its twigs.
How did it arrive here?
Like many invasive plants in North America, glossy buckthorn was intentionally planted in home gardens because of its height and dense foliage, which could be used as an effective privacy hedge. It was thought to be brought over in the 18th century for this purpose from its native habitat of Eurasia. The first recorded collection of glossy buckthorns outside of domestic cultivation was in 1934. Since then it has become a much bigger issue in the northern United States and Canada. Acadia’s first superintendent, George B. Dorr, listed glossy buckthorn in his families’ Mount Desert Nurseries catalog in 1900. Located at Oldfarm, near Compass Harbor. Glossy buckthorn grows among the historic nursery grounds to this day.
Why is it invasive?
Glossy buckthorn does very well in bright, open spaces, such as wetlands, pastures—especially along fence paths—and open woods. What sets it apart from other invasive species is its ability to colonize without disturbance. Many invasive plant species (i.e. honeysuckles, Japanese Knotweed, etc.) require soil disturbance to take root and become effective invaders, whereas glossy buckthorn does not require this. Because of this, it can establish populations almost anywhere that has enough moisture, including Acadia's summit seeps, salt marsh edges, and everywhere in between.
Like many invasive shrubs, glossy buckthorn is dispersed by either animals or water. The fleshy fruits are very attractive to birds, so they can travel far distances this way. Fruit production is best when the plant is growing in open spaces with plenty of sun, sometimes only taking 2-3 years for stems to reach maturity. Glossy buckthorn’s dense foliage and ability to mature quickly, allows it to outcompete most of the other low growing shrubs, tree seedlings, and herbaceous plants around it. This decreases the biodiversity of some of our most important wetlands and young forests.
Management at Acadia
Glossy buckthorn is very carefully monitored by the Invasive Plant Management Team (IPMT) at Acadia and resource managers have prioritized its removal for more than a decade. It has been detected in several wetlands and new-growth forests throughout the park, most notably in Great Meadow and Kent Field. It has also been found along roadways and in abandoned fields.
In August 2020, the IPMT started removing glossy buckthorn from the Bass Harbor Marsh area. In the coming years, the IPMT will continue to return to this and other sites to monitor the changes in vegetation, and continue to control the invasive shrub. The IPMT follows a multi-year plan that involves the use of wetland-approved herbicides as well as cutting and stump removal to prevent new regrowth. Herbicide application is specifically timed to prevent the production of fruits, so that there is less dispersal throughout the park.
Public reporting of glossy buckthorn bushes within the park is highly encouraged by the IPMT. Removal of bushes on private property is also encouraged to decrease the overall population size and impact on natural resources. Visitors to the park should refrain from disturbing the bushes when they are flowering or have fruit, since this may encourage seed dispersal. Landowners can also plant native shrubs, trees, and flowers on their property in place of non-native invasive plants.
Duym, Ericka B. 2016. “Cultural Landscape Inventory and Assessment for Oldfarm”. The Somes Pond Center, Mount Desert, ME.
Michigan Department of Natural Resources. 2012. “Glossy buckthorn (Frangula alnus)”. Michigan Natural Features Inventory 2: 1-8. https://mnfi.anr.msu.edu/invasive-species/GlossyBuckthornBCP.pdf
Reinartz, James A, and Joanne Kline. 1988. “Glossy Buckthorn (Rhamnus Frangula), a Threat to the Vegetation of the Cedarburg Bog.” Field Station Bulletin 21(2): 20-35. https://dc.uwm.edu/cgi/viewcontent.cgi?article=1128&context=fieldstation_bulletins