Currently Palmer amaranth is known to be present in five Iowa counties (Harrison, Fremont, Page, Lee and Muscatine). The similarity of Palmer amaranth with waterhemp greatly complicates finding new infestations, especially early in the season (Figure 1). In the vegetative stage many characteristics within the species are indistinguishable. The long petioles on Palmer amaranth are a good trait to differentiate, although occasionally waterhemp exhibits this trait. The only foolproof method is to examine the flowers of the two species.
Iowa State University
Hartzler, Robert G. and Anderson, Meaghan J. B., "Keep eyes open for Palmer amaranth" (2015). Integrated Crop Management News. 1494.
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