Invasive Species

Dark blue berries of buckthorn and orange lesions of oat crown rust on buckthorn leaves.
If you've seen a forest thick with Common Buckthorn (Rhamnus cathartica), you know what an invasive plant does. It takes over.

Formally defined, an invasive plant is one that is introduced (it isn't native to the area) and that causes harm by its growth and spread. The harm could be to the environment, to the economy, or to human health -- or all three. 

Buckthorn checks all those boxes. Since it was introduced to the U.S. in the late 1700s, it has spread throughout most of the country, forming dense thickets that reduce plant diversity and animal habitat. It's a pushy plant, and prolific, too. One female can produce hundreds of dark, berry-like fruits, each containing two to four seeds. Birds eat the fruits and deposit the seeds in their droppings, and so buckthorn spreads.

Buckthorn's damage isn't limited to the forest understory. It's also an alternate host for soybean aphids and oat crown rust (a fungus), two pests that can drastically reduce the yield and quality of these crops. Each pest spends part of its life cycle on the crop and another part on buckthorn. Without both hosts, the pests can't survive.

As for human health, buckthorn's direct effect is primarily through its fruits. The dark, shiny clusters of fruits can be mistaken for chokecherries or other edibles, but with bad results. Eating them has a cathartic effect on the digestive system -- thus the scientific name cathartica and another common name, purging buckthorn. The more fruit or seeds eaten, the greater the effect, and as you might guess, it's unpleasant.

Many introductions are harmless, but some plants, like buckthorn, have a similar story of arrival, aggressive spread and eventual harm to natural or managed environments, the economy or human health. A first step to reduce their impact is to prevent their introduction and halt their spread, and the first step to that is to build awareness.  

To that end, below are links to projects and information about invasive species. Some of them cover introduced animals and pathogens as well as plants. Many also provide general information about invasive species. 

Volunteer and Community Science Opportunities  

Report garlic mustard aphids. The Midwest Invasive Plant Network is asking citizen scientists to look for garlic mustard aphids, Lipaphis alliariae. These small black insects appear to damage the seed pods and leaves of garlic mustard (Alliaria petiolata) and may be an agent for biological control. Garlic mustard aphids have been confirmed in Minnesota, according to EDDMapS. Further mapping will help determine the extent of their spread and their impact on garlic mustard. To learn more, click or tap on the header link above. 

Three Rivers Park District Rapid Response and Early Detection (R2ED) Team. Led by the District's invasive species coordinator, the R2ED team is a group of volunteers engaged in finding and removing invasive plants from Three Rivers Park District. Individual and group efforts are welcome, and training is provided. The District is a regional system of parks, trails and recreational areas in the Twin Cities metropolitan area. Locations

Wisconsin First Detector Network (WIFDN). Coordinated by the University of Wisconsin-Madison, WIFDN enlists volunteers for invasive species "monitoring, management and outreach." Online training is provided. 

Wildlife diversity and community science. The Minnesota DNR needs volunteers for several projects involving wildflife. Directly or indirectly, many of them also involve plants.

Education & Training
InvasivesU Online Learning from the North American Invasive Species Managaement Association (NAISMA). 

Species Training Modules from the Midwest Invasive Species Information Network (MISIN).

Educational materials from the Midwest Invasive Plant Network (MIPN)

Homeowner's Guide to Invasive Plants from NWS Real Estate (Thank you, Lakeville environmental science students, for suggesting this resource!)

Checklist of Common Invasive Plant Species from Blue Thumb and Ramsey-Washington Metro Watershed District

Midwest Invasive Plant List from Midwest Invasive Plant Network

Emerging Midwest Invasives. Learn about new invasive plants from this 2023 series of recorded webinars from the Midwest Invasive Plant Network (MIPN). 

Scroll down to "Newsletter Sign Up."


This site includes a public data dashboard showing which horticultural species are or may become invasive.

Noxious and Invasive Weed Program - Minnesota Department of Agriculture

Minnesota Noxious Weeds - Minnesota Department of Transportation

Invasive Terrestrial Plants - Minnesota Department of Natural Resources

A Field Guide to Terrestrial Invasive Plants in Wisconsin - Wisconsin Department of Natural Resources

Woody Invasives of the Great Lakes (WIGL) Collaborative - Great Lakes Restoration Initiative

Midwest Invasive Plant Network (MIPN) - Morton Arboretum, Illinois

Species- or Group-Specific Guides

Identifying Phragmites - Minnesota Aquatic Invasive Species Research Center, University of Minnesota

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