Invasive Species

• Background: This is a restricted noxious weed and is illegal to import, sell, or transport within Minnesota. Buckthorn was first brought over to Minnesota from Europe in the 1800s to be used as a popular hedging species. They commonly grow in oak savannah, prairie, or riparian areas. Its rapid and aggressive growth can quickly crowd-out native species, ultimately decreasing forest diversity. 

• Description: Tall understory shrub with a loosely-branched crown with multi-stem base. Bark is brown with silver corky projections (similar to what you would find in other cherry of plum trees).Twigs can have small, sharp thorns. Leaves can be alternate, opposite, or sub-opposite; broad elliptic shape; finely serrated; with dark gloss. Flowers are small, green, and clustered on leaf axils. Fruit are small, black, and in clusters.

• Management: Buckthorn can be removed using both mechanical and chemical means. See the MN Department of Natural Resources page on buckthorn for control methods.

Emerald Ash Borer (EAB) was discovered in the Rochester area in August of 2014 and in the Rochester city limits in 2015. Learn more on the Emerald Ash Borer page.

Background: Like common buckthorn, this species is also a restricted noxious weed and was brought over from Europe. There are three different nursery cultivars for this species. They commonly grow in wetlands, fens, or sedge meadows. They too have aggressive tendencies that can crowd-out native species and decrease forest diversity.

Description: Tall understory shrub with a loosely-branched crown with multi-stem base. Both buds and leaves are alternate. Bark is brown with silver corky projections (similar to what you would find in other cherry of plum trees). Leaves are dark and glossy with smooth edges.

Management: Buckthorn can be removed using both mechanical and chemical means. See the MN Department of Natural Resources page on buckthorn for control methods.

Background: This is a restricted noxious weed and is illegal to import, sell, or transport within Minnesota; thus, presence of this species any property is a city violation according to Ordinance 8-5. Within Minnesota alone, there are seven thistle species with three of those being invasive. These include Canada thistle, Bull thistle, and Plumeless thistle. All species can be found in disturbed areas such as along roadsides, ditches, or within prairies. 

Description: All species grow around 2-5 feet tall and are distinctive by the 'thistles' or spines that grow from their stem and leaves. Purple flowers are also a distinctive feature of this genus.

Management: Mechanical means of control include repeated pulling, mowing before flower bloom, and consecutive late spring burns. Chemical means include spot application with glyphosate or with selective herbicide clopyralid, or metsulfuron. Biological control includes weevils or stem gall fly.

• For more information on Bull thistle, visit the UMN Extension Bull Thistle page.
• For more information on Canada thistle, visit the MN DNR Canada Thistle page.
• For more information on Plumeless thistle, visit the MDA Plumeless Thistle page.

Background: This is a restricted noxious weed and is illegal to import, sell, or transport within Minnesota; thus, presence of this species any property is a city violation according to Ordinance 8-5. This species was cultivated by European settlers in the US as a root vegetable. Wild parsnip can quickly grow into a monoculture in disturbed landscapes and crowd-out any natives. Plant sap of this species contains toxic chemicals that cause blistering or burns on skin when exposed to the sun.

Description: Will grow up to 4-6 feet with hollow stem. Leaves are alternate, serrated, pinnately compound, with pairs of leaflets up the stem growing smaller towards the tip. Flower is in the shape of an umbel (2-6 inches wide) made up of several small 5-petaled flowers.

Management: Mechanical means of managing this species include hand pulling, mowing, and cutting. Chemical means include spot treatment using glyphosate. 

• For more tips on identification, visit the MISIN wild parsnip ID guide.
• For more information on treatment, visit the MDA treatment guide.