In 2015, common buckthorn (Rhamnus cathartica) became the first county listed noxious weed in Missoula County. The process involved with listing common buckthorn began early in the year when an application form was sent to local land managers requesting submissions for species not on the state list that they thought had noxious qualities. Common buckthorn was the only species submitted for consideration. The application was submitted by the City of Missoula Open Lands Program (OLP). The OLP had found common buckthorn along the majority of waterways within and adjacent to the 4,000 acres of land they manage.
Working to eradicate this species requires a long-term commitment because common buckthorn can grow to be a multi-stemmed tree capable of producing thousands of fruit each year. Inside each fruit there are one to five seeds. The oldest common buckthorn found in Missoula County thus far had 67 identifiable annual growth rings.
Seed dispersal for this species is primarily through birds. Fruit is attractive to birds, but contains little nutritional value and causes a cathartic reaction in birds that eat common buckthorn seeds, aiding in dispersal. Seed longevity ranges from two to six years.
Fruits have the ability to float, especially when dry, and can be dispersed along waterways. Common buckthorn also has the ability to re-sprout from stumps and fibrous root mats after cutting. These characteristics make common buckthorn a challenge to control.
Over the past few years managing this species on city land, the OLP had identified a four-acre parcel along Rattlesnake Creek as the heart of the infestation. In 2015 the Missoula County Weed District (MCWD) contacted landowners adjacent to this area of infestation to start educating and developing removal strategies for landowners with common buckthorn infestations. Working with these landowners over the past year, MCWD staff and participants in the Youth in Restoration program pulled and disposed of small-diameter fruit producing buckthorn throughout the growing season. In the fall MCWD staff, OLP staff and a crew from the Montana Conservation Corp cut down large diameter common buckthorn trees. Stump treating the base of each trunk with an herbicide immediately after to prevent re-sprouting.
The MCWD will continue to focus our control efforts on this area of infestation for the next few years. During this time, we hope to learn how to effectively control common buckthorn in our area in order to provide well-informed recommendations to landowners and managers.
In addition to these control efforts, the MCWD also implemented a mapping effort, in collaboration with students in the Restoration Ecology capstone project at the University of Montana, to identify where common buckthorn is currently growing in Missoula County. These students surveyed for common buckthorn at fishing access sites across the county and along creek drainages throughout the Missoula Valley. Through this effort they found hundreds of new common buckthorn infestations.
During the fall of 2015 information on the life history, invasive potential and abundance of common buckthorn was presented to the Missoula County Weed District Advisory Board. The Advisory Board took this information into consideration and decided that common buckthorn warranted listing as a County Noxious Weed. Following a positive public hearing, common buckthorn became the first County Listed Noxious Weed in Missoula County. Once this species was listed at the county level, a request was submitted to the State Department of Agriculture to consider common buckthorn, which is currently found in over half of the counties in Montana with known areas of invasion in six counties, as a candidate for state listing as a noxious weed. Common buckthorn is also currently listed as a noxious weed in six northern states.
Common buckthorn is not our first advisory and it will not be our last. Requests will be sent out to local land managers on an annual basis requesting suggestions of species that warrant listing. Through this process the MCWD will be able to effectively respond to new invading noxious weeds, decreasing the negative impact these species can have on our ecosystems and economy.
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