There are a number of invasive plants in the Twin Ports. Duluth is officially trying to eradicate Buckthorn, Japanese Knotweed and Garlic Mustard. The City sponsors a volunteer group called "Duluth Invaders". Click link for info on how to get involved.

Japanese Knotweed

Japanese Knotweed"With a bamboo-like appearance, Japanese Knotweed was brought from Asia to the US in the 1800’s. The plant outcompetes native vegetation and greatly alters natural ecosystems, particularly along riparian zones. Bamboo has an ability to survive floods, and, quickly colonizes scoured shorelines and islands damaged in flood events. Japanese Knotweed is difficult to control. It is a perennial plant that dies back to the ground each year, and then grows to heights of ten feet or more, often growing several inches in height per day."  

Garlic Mustard

Garlic MustardTypically, garlic mustard flowers arrive in late April to early May. The weed is among the most noxious in Minnesota, forming a dense carpet that can crowd out tree seedlings and native wildflowers. It is particularly troublesome because it infests shaded areas, which is unusual for invasive plant species. Its appearance is characterized by small, round, scalloped-edged evergreen leaves in its first year. Second-year plants have larger, arrow-shaped leaves. The second-year plants also bolt to heights of up to two feet and produce a small, white, four-petaled flower.  The leaves and stems of the plant will smell like onion or garlic when crushed."  

(Above information copied from Duluth city web page Garlic Mustard and Japanese Knotweed. Contact City of Duluth Parks and Recreation Division for organized eradication events.)
 

Buckthorn

Buckthorn was originally introduced as a hedging plant. It is now invasive in city parks and wooded areas.  It's not uncommon to see it in private yards, as well.  The import, transport, and sale of buckthorn in now illegal in Minnesota. 

Scilla siberica (Siberian Squill)

This bulb plant has a lovely little blue flower and is one of the first things to pop up and bloom in the Twin Ports area Spring. The problem is it is invasive; in particular, local wildlife will not eat it, and it can prevent native plants from regenerating . Along Chester Creek in Duluth, it has hopped from residential properties over to the creek, where it appears to be gaining a foothold. It is a good idea to remove as much of the plant as possible before it goes to seed. Large tracts can be mowed, but clippings should be disposed of. Avoid composting.

Siberian Squill

For more info: 

http://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/japaneseknotweed.html

http://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/garlicmustard.html

http://www.minnesotawildflowers.info/flower/siberian-squill