Minnesota Noxious Weed Program

The MDA Noxious & Invasive Weed Program assists local governments and landowners with resources for managing noxious and invasive weeds throughout Minnesota. Strong partnerships exist between the MDA and County and local government partners to enforce the Minnesota Noxious Weed Law.

Per the Minnesota state Statue Section 18.83: all persons in shall control or eradicate all noxious weeds on land they occupy or are required to maintain. Control or eradication may be accomplished by any lawful method, but the methods may need to be repeated in order to prevent the spread of viable noxious weed seeds and other propagating parts to other lands.


To learn more, visit the MDA website (https://www.mda.state.mn.us/plants-insects/noxious-invasive-weed-program) or contact our office.



A Few of the Noxious Weeds in Wadena County... 

Common Buckthorn

Common Buckthorn is a dioecious shrub that can grow up to 25 feet tall with potential to become a small tree. Its leaves are sub-opposite with veins curving to the tip of the leaf and will remain green in autumn. The fruit is a small, purplish-black, berry-like fruit and is grown only on female plants. Mostly found in an understory or on a forest edge and will out-compete native species.


Comparison Tip: Small, 4-parted, green flowers

Common Tansy

Common Tansy is a perennial that can reach up to 5 feet in height. Its stem appears woody and is purplish-red at the base. The leaves are aromatic when crushed as well as the yellow button-like flower heads. This plant is often found in dry, open, disturbed areas such as trail edges, roadsides, and old pastures.



Comparison Tip: Lack of ray petals surrounding the flower head in comparison to native goldenrods.

Leafy Spurge

Leafy Spurge is a perennial that grows up to 3 feet tall and displays blueish-green foliage. Its small flowers are yellow-green in color and do not contain any petals or sepals. This perennial will invade dry sites in full sun but can tolerate other conditions.



Comparison Tip: Produces a milky sap when stem or leaves are broken.


Spotted Knapweed

Spotted Knapweed is a perennial living up to 4 years. Its initial stage is a rosette before it produces multiple stems up to 4 feet tall. Its leaves are alternate with a grayish-green color and deep sinuses while its flower resembles a thistle’s. This plant prefers to grow in sandy or gravely disturbed sites.



Comparison Tip: Stiff brats with dark-haired tips.


Plumeless Thistle

Plumeless Thistle is a biannual growing up to 4 feet tall. Leaves are attached directly to the stems and typically have hairs on the bottom along the mid-vein. This plant produces numerous branches to display single, terminal pink to purple flowers with bracts full of short spines. Can be found on dry to moist sites including pastures, woodlands, and roadsides.


Comparison Tip: Stems are winged and spiny.


Wild Parsnip

Caution: Contact with the sap of the plant when exposed to sunlight can cause extreme blistering and swelling. Handle with gloves and long sleeves. 


Wild Parsnip is a perennial classified as a monocarpic, meaning the plant dies after bearing fruit and usually lives about 2 years. Initial stage is a basal rosette before developing into a hollow, grooved flowering stalk stretching up to 5 feet upon maturity. Basal leaves are pinnately compound, containing 5-15 leaflets while the stem leaves are alternate with 2-5 leaflets. Its flowers are small and yellow with 5 petals on wide, flat umbels. This plant is usually found in drier, full sun to part shade habitats such as roadsides and abandoned fields, but it can also invade a wet meadow.


Comparison Tip: The base of the leaf stalks wrap/clasp the grooved stem.



Canada Thistle

Canada Thistle is a perennial with grooved, hairy stems reaching up to 6 feet tall. Its stalkless leaves are irregularly lobed with toothed, spiny edges whose undersides turn downy or hairy at maturity. Displays a disk-shaped flowerhead that eventually form tuft, light brown seeds that are dispersed in the wind. This thistle can invade any disturbed area including roadsides, fields, and woodlands.


Comparison Tip: Stems and bracts are non-spiny.

Purple Loosestrife

Purple Loosestrife is an aquatic perennial that can reach up to 6 feet tall and display densely packed purple/pink flower spikes. Individual flowers grow 5-7 petals, each appearing wrinkled while also containing a dark vein down the middle. Its stem is square and covered in downy hair while opposite or whorled leaves contain no stalk and are rounded/ heart shaped at the base and pointed at the tip. The plant prefers to grow in wet areas mixed with full sun such as marshes, ditches, and shorelines.


Comparison Tip:  5-7 petals on flowerheads. 

Additional Plant Resources:

Pesticide Testing

It is the Minnesota Department of Agriculture's (MDA) policy to allow pesticide applicators to be tested by their County Agricultural Inspector (CAI). The CAI assists in the testing of pesticide applicators to ensure that pesticide applications within the County are conducted by properly trained and licensed personnel.



Need study materials? Order them here (https://bookstores.umn.edu/books/pesticide-manuals) or call 612-301-3989.


Additional Resources