Jared Goplen, Extension educator - crops
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Long seed head of Palmer amaranth. Photo: Lisa Behnken |
Identification characteristics of Palmer amaranth
Early detection and eradication of Palmer amaranth is key in reducing management costs and preventing the rapid spread of this difficult weed. Palmer amaranth is challenging to identify as many of the amaranth species (waterhemp, redroot pigweed, etc.) look similar. However, identification is easier as plants enter the reproductive phase of development, which is occurring now through September. For help in identification, please go to the following web link: http://z.umn.edu/palmerid.![]() |
Photo 1. Spiny bracts of female Palmer amaranth plant. |
Key characteristics to look for include:
- Plant is smooth with no hairs on stems or leaves
- Leaf petiole (the stalk connecting the leaf to the stem) is often longer than the leaf
- Seed and pollen heads can reach 1 to 3 feet in length, which is longer than other amaranth species.
- The most consistent characteristic is the spiny bracts found on the female seed head (Photo 1).
Sources of contamination
So far in Minnesota, confirmed contamination sources of Palmer amaranth have included: 1) native seed/pollinator planting mixtures, 2) contaminated manure (from contaminated sunflower screenings), and 3) contaminated cover crop seed. Several contamination sources where Palmer amaranth was confirmed are still unknown, but numerous other contamination sources exist. A list of common contamination sources includes:- Contaminated crop / cover crop seed (especially seed produced where Palmer amaranth is common)
- Contaminated equipment
- Used equipment recently purchased (especially from outside the region)
- Custom farm equipment (especially custom combines)
- Contaminated manure / feed ingredients
- Sunflower screenings
- Cottonseed
- Purchased hay and straw
- Any other byproduct feed ingredients produced where Palmer amaranth is more common
- Wildlife
- Migratory birds are capable of transporting Palmer amaranth and other weed seeds long distances.
Status of Palmer amaranth in Minnesota
An interactive map about the presence of Palmer amaranth throughout Minnesota, including sources of contamination and year of last detection can be found at: https://z.umn.edu/Palmer-amaranth-status-MNReporting Process
If you or your crop consultant suspect the presence of Palmer amaranth, the MDA and University of Minnesota Extension (U of MN) suggest the following reporting process:- Take pictures of the plant(s) in question before pulling them. Pictures should include clear visibility of the whole plant, a close-up of the leaf and where it attaches to the stem, the flower head, and a leaf with the petiole folded over.
- Save plants in a refrigerated plastic bag for any genetic testing that may be needed.
- Report the find to the Minnesota Department of Agriculture’s Arrest the Pest line at 1-888-545-6684 or arrest.the.pest@state.mn.us. UMN Extension Educators are available to assist in this process as well.
For more information
For more information regarding Palmer amaranth and its management, visit:
https://extension.umn.edu/annual-broadleaf-weeds/preventing-palmer-amaranth-minnesota
https://extension.umn.edu/annual-broadleaf-weeds/preventing-palmer-amaranth-minnesota
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