Sachin Dhanda and Sithin Mathew engage with a Palmer amaranth experiment, St. Paul, MN
Background
Palmer amaranth (Amaranthus palmeri) is the most problematic weed in row-crop production in the US. It was first reported in Minnesota in 2016. Because the species is on the Minnesota Prohibited Noxious Weed Eradicate list, it has not been feasible to conduct field experiments, and there is a lack of information about how the species adapts and competes in Minnesota which would inform management strategies. This is further underscored by climate change as Minnesota experiences wetter springs, more common flash floods, and drought in summer.
Palmer amaranth is receiving some competitive challenge from its native relative, waterhemp (Amaranthus tuberculatus). Waterhemp is well-established in Minnesota. The two species have many biological and physiological commonalities, however there is limited data on their relative competitiveness when they coexist, especially in the same climate.
Research question
- How do changes in precipitation/soil moisture influence the emergence and growth of Palmer amaranth?
Outcomes
Across experiments, neither Palmer amaranth nor waterhemp survived complete flooding. However, Palmer amaranth is more likely to thrive in water-stressed environments than waterhemp, which is not what was previously assumed. This provides important information on the adaptability of Palmer amaranth to current and future rainfall patterns in Minnesota, with its potential to spread under changing climate conditions.
Outreach
- Palmer amaranth ID, distribution, and management options through U of M Extension, 2024
- Upper Midwest Invasive Species Conference, 2024
- Weed Science Society of America Conference, 2025
News and media
- The unyielding weed: Palmer amaranth (MITPPC, 2025)