Waterhemp: A ‘Friendly’ Native Evolves Into the Cornbelt’s Worst Weed Problem
Waterhemp’s rise to the Cornbelt’s worst weed is one of the Cornbelt’s more fascinating weed-related events over the past 40 years, writes Extension Weed Specialist Bob Hartzler at Iowa State University Extension and Outreach. Waterhemp (Amaranthus tuberculatus) is native to the U.S. but is a relative newcomer to crop fields. Prior to waterhemp’s ascent, redroot pigweed (A. retroflexus) and smooth pigweed (A. hybridus) were the pigweed species most commonly found in crop fields. Pammel (1913) described redroot pigweed as abundant in every Iowa county, whereas he stated waterhemp (A. tuberculatus) was found along water courses and marshes, and concluded the plant was “not long present in well cultivated fields”.
In this article, Hartzler briefly describes the history of the pigweeds in the region, and discusses the management and genetic factors that accompanied the change in waterhemp’s behavior as a weed. I use the term ‘weedy waterhemp’ to describe the biotypes that currently plague agricultural fields.
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