Report a Pigweed

Report a Pigweed Update!

Thank you everyone for reporting pigweeds that you found this year. We received 48 new reports of Waterhemp and 4 reports of Palmer Amaranth found in Wisconsin through the Report a Pigweed program.

Thank you so much for participating and please keep reporting pigweeds next year!

Have a pigweed? Do you believe it may be waterhemp or Palmer amaranth? Watch this pigweed identification video on vegetative characteristics to learn how to identify and report them!

Do you have a pigweed that’s already flowering? This video on flowering characteristics will tell how to differentiate among pigweed species found in Wisconsin.


Pigweeds include many species of the genus Amaranthus that grow as annual summertime weeds. The goal of this project is to identify the location of two extremely problematic pigweeds – Palmer amaranth (fact sheet) and waterhemp (fact sheet). These two species have developed resistance to commonly used herbicides in agronomic settings in Wisconsin, making it difficult for farmers to control their spread.


You! We need everyone’s help to report locations of these two super pigweeds in Wisconsin. While we are focused on agricultural fields, we still want positive identifications of either waterhemp or Palmer amaranth from any habitat, because they grow very well in a hot climate.

You’ll be able to find pigweeds anywhere because they grow so prolifically. This causes them to out grow other species and grow in many varying conditions.


Tracking the location of these pigweeds in Wisconsin is vital to efforts to stop the spread of these problematic species across our natural and agricultural landscapes. These weeds are sometimes considered super-weeds, being able to disperse more seeds, wait later to emerge, and have higher growth rates than most other pigweeds. This results in lower crop yields and the use of more chemicals in agricultural fields. Many pigweed populations in the Midwest are also developing herbicide resistance. Palmer amaranth and waterhemp are dioecious plants (separate male and female plants), which means they can exchange genetic information easily, allowing them to develop herbicide resistance more rapidly than other species.

Check out this video about why we should care about reporting our pigweeds found in Wisconsin!


Everywhere! You can look anywhere for these pigweeds. Currently, the biggest concern is in agricultural settings, but Palmer amaranth and waterhemp also grow along roadsides and in gardens, among other habitats. The maps below show confirmed reports of waterhemp and Palmer amaranth through 2017.







Palmer amaranth and waterhemp are summer annuals, so it will be easiest to identify and report these species starting in the summer.


The ?’s (and Answers!) on Reporting a Pigweed

If you believe you have Palmer amaranth or waterhemp, please report it. Your reports help track these pigweeds in Wisconsin and improve efforts to limit their spread. There are a few ways to report a pigweed:

Option 1:

We recommend using the Great Lakes Early Detection Network (GLEDN) app. Go to the Google Play (Android users) or the App Store (Apple/iOS users) and download the GLEDN app. Find more information about reporting with the GLEDN app here.

Option 2:

If you do not wish to download the GLEDN app, you can report your pigweed by emailing us at and include these pieces of information:

1) Location of the pigweed: GPS coordinates (in decimal degrees; NAD83 or WGS84) or an address/road intersection

One way to find GPS coordinates is to visit Google Maps. Right click on the location of the plant(s) and select “What’s Here?”. A gray marker will appear and the coordinates (in decimal degrees) will be displayed at the bottom of the screen.

To report an address/road intersection, please include an additional description. For example, “100 feet southwest of the intersection of County Rd DL and Hwy 113 in Merrimac” or “200 feet east of 1151 Observatory Drive in Madison.”

2) The habitat where the pigweed is growing: agricultural field (indicate what type of field, e.g. corn, soybean, etc.), home garden, roadside, or other (please describe).

3) Indicate whether the plant may be herbicide resistant, and if so, what herbicide has been applied.

4) Pictures of the pigweed, including a picture of the whole plant, a picture of the plant stem, and a picture of the leaf and petiole (leaf stem).

Include one close-up picture of the stem to show it does not have hairs.

Include one close-up picture the petiole (leaf stem) folded over the leaf to show whether the petiole is shorter or longer than the leaf.


Thank you for your participation in Report a Pigweed!