By Wayne Flanary
Palmer amaranth is slowly advancing in Northwest Missouri; however, hopefully we can continue to slow its spread to new fields. If you see large pigweed species plants, now is the time that you can more easily identify it from waterhemp.
Once Palmer amarantha flowers, it has long, sharp bracts surrounding the flowers. When you grab them, you will get stuck. A couple of years ago I realized this as I was looking for glyphosate resistant Palmer plants and wished I had gloves.
Also, the petiole is typically longer than the leaf blade. You can fold the leaf and petiole and measure this. However, there is a lot of variability in species.
If you find plants in the field, remove them so they cannot go to seed. Palmer and waterhemp both produce thousands of seeds per plant.
For more information, contact Wayne Flanary, Field Specialist in Agronomy, at 660-446-3724, University of Missouri Extension.