June 2017 Vol. 25, No. 2

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Help eradicate dangerous plants from Minnesota

Thirteen plant species are currently on Minnesota's eradicate list. "These species are known to cause environmental or agricultural harm in Minnesota and other states," says Dawn Littleton, Minnesota Extension invasive plants program coordinator.

Three of the species to watch for are shown below. The full list and additional information (including videos) are online. Be sure to report any sightings immediately—see the "Arrest the Pest" article below.

If you would like a class on identifying any plant that is causing concern, please contact Littleton at 507-536-6301, litt0129@umn.edu. Extension also holds classes in the spring.



Palmar amaranth. Photo: Minnesota Extension


Oriental bittersweet. Photo: Minnesota Extension


Diffuse knapweed. Photo: Minnesota Extension

Palmar amaranth. This fast-growing weed, native to the southwestern United States and northwestern Mexico, is a summer annual. Its green leaves are smooth and arranged in an alternate pattern that grows symmetrically around the stem. It looks similar to our native pigweeds such as tall waterhemp, redroot, and smooth pigweeds. It has developed resistance to multiple classes of herbicides and their different modes of action, making it very difficult and expensive to control. It grows 2 to 3 inches per day and commonly reaches heights of 6 to 8 feet, greatly inhibiting crop growth. Reported yield losses have been up to 91% in corn and 79% in soybean in some states. The weed can also significantly increase production costs for corn, soybean, and other crops. In September 2016, Palmer amaranth was initially discovered and confirmed in Minnesota. Thirteen sites have been documented in Yellow Medicine and Lyon Counties.

Oriental bittersweet. This climbing vine is found in forested areas, field and forest margins, meadows, rights-of-way, fence rows, along waterways, and in residential landscapes. The vines girdle and smother trees and shrubs. In addition, the added weight of the vines covered with snow and ice can break trees and shrubs. The leaves are green, then turn yellow in the fall. Fruits are round and change in color from green to bright red with a yellow capsule as they mature. Infestations have been confirmed in Winona and the Twin Cities.

Diffuse knapweed. This biennial plant thrives in disturbed habitats such as roadsides, railroad tracks, gravel pits, vacant lots, and heavily grazed pastures. Leaves are covered with short dense hairs, giving the plant a gray tint. Flowers are usually white but sometimes pink or purple. This knapweed is widespread throughout rangeland in the western U.S., but in Minnesota the only known infestation is in St. Louis County. Diffuse knapweed overtakes and suppresses native vegetation, reducing species diversity and wildlife habitat. It can also increase soil erosion and cause crop loss and reduced forage for livestock. The spines on the flower heads can damage the mouths and digestive tracts of livestock.