Skip Navigation  9/2/2013 - 9/8/2013  Identifying waterhemp and
Palmer amaranth  By Bob Hartzler, Department of Agronomy
Several people have submitted images of escaped "pigweeds"
wondering whether the plants were Palmer amaranth. In all cases,
except the earlier reported situation in Harrison County, the
plants in question have been waterhemp, although at casual
glance they could easily be mistaken for Palmer amaranth. These
cases highlight the difficulty in differentiating the two
species by the general growth habit and shape of plants.  Palmer
amaranth is generally characterized by longer and thicker
terminal inflorescences (flower stalks) than found on
waterhemp. However, both species are highly variable and there
is much overlap in their general appearance. With many waterhemp
control failures across the state due to herbicide resistance,
the entire phenotypic variation of waterhemp is on display, and
there often are plants present that have inflorescences typical
of Palmer amaranth. I have seen numerou