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Palmer Amaranth

Scientific Name

Amaranthus palmeri S.Watson  (ITIS)

Common Name

Palmer amaranth, palmer pigweed, carelessweed

Native To

Southwestern U.S. (Ward et al. 2013)

Date of U.S. Introduction

First reported outside of its native range in Virginia in 1915, but was not a significant weed in the Southeast until the 1990s (Ward et al. 2013); glyphosate-resistant varieties first appeared in 2004 (Culpepper et al. 2006)

Means of Introduction

Most likely through the transport of contaminated seed; some recent infestations in the Midwest were caused by contaminated Conservation Reserve Program seeding mixes (Ward et al. 2013; Murphy et al. 2017)

Impact

One of the most economically important weeds of corn, cotton, and soybean; some populations are resistant to glyphosate and other herbicides (Ward et al. 2013)

Palmer amaranth

Palmer amaranth in field

Credit

Howard F. Schwartz, Colorado State University

Find more images

Spotlights

  • Understanding the Science Behind Pigweed’s Amazing Adaptation

    • Dec 20, 2021
    • USDA. ARS. Tellus.

    • Pigweed is a major challenge to our farmers and growers. It is extremely resilient and resistant to many herbicides, posing a significant threat to the agriculture industry. ARS scientists in Stoneville MS, along with collaborators from Clemson University, are researching the pigweed itself to find ways to mitigate this highly adaptable weed.

  • Pigweed is No Match for DNA Testing

    • Jun 29, 2017
    • USDA. National Institute of Food and Agriculture.

    • Last summer, farmers in the Midwest got an unwelcome surprise after planting native seed on Conservation Reserve Program acres: Palmer amaranth (aka Palmer’s pigweed), an aggressive and hard-to-kill weed that is native to the Southern United States. Pat Tranel, molecular weed scientist at the University of Illinois, noted that growers who sell seeds are in jeopardy due to the spread of this noxious weed. “Unless they have a way to certify their product is Palmer-free, they can’t sell it,” Tranel said. Tranel and graduate student Brent Murphy developed a way around these issues. Their low-cost method can identify Palmer amaranth DNA from within a mixed sample without having to grow the plants. This project was made possible with support from NIFA.

  • Watch Out for Palmer Amaranth in Your Conservation Plantings

    • Mar 2017
    • USDA. Natural Resources Conservation Service.

    • An invasive species is on the move and may be headed for Montana. Palmer amaranth, a giant pigweed, is known to have spread to at least 28 states, including Minnesota and South Dakota, but has not yet been reported in Montana. To prevent its spread into Montana, landowners are encouraged to check their fields to ensure the invasive weed is not present. It was a known contaminant in Conservation Reserve Program (CRP) seed mixes but pollinator, wildlife habitat and cover crop plantings may also been contaminated. Producers with recent conservation plantings should check their fields to ensure this invasive weed is not present.

  • Climate Change Impacts on Palmer Amaranth

    • United States Department of Agriculture. USDA Climate Hubs.

    • Palmer amaranth (Amaranthus palmeri S. Watson) is an annual plant in the pigweed family (Amaranthaceae). It is native to the southwest United States/northern Mexico deserts and is currently increasing its range across the country. USDA NRCS, their partners, as well as farmers and landowners are working to eradicate these infestations before they spread to new areas. Midwest Climate Hub fellow, Dr. Erica Kistner-Thomas is getting a jump on how the distribution of Palmer amaranth will change from current to future climate conditions. Climate change is going to benefit this heat-tolerant weed by lengthening its growing season, boosting seed production and expanding its potential U.S. geographic range.

Distribution / Maps / Survey Status

Videos

Selected Resources

The section below contains highly relevant resources for this species, organized by source.

Partnership
Federal Government
International Government
State and Local Government
Academic
Citations