How To Identify Palmer Amaranth

Palmer amaranth, a pigweed cousin, is one weed worth finding and removing now.

Published on: Jul 18, 2013

Two years ago Dow AgroSciences flew journalists to the Deep South for the first day of a two-day field day, then finished it in plots northwest of Indianapolis the next day. Why go to the South? Primarily to introduce them to Palmer amaranth, an aggressive cousin of other pigweeds. It produces several times the amount of seeds per plant compared to other pigweeds.

I didn't go on the trip – I don't fly. But my colleague, Josh Flint, Prairie Farmer editor, did. He assured me it was every bit as wicked as they said it was.

Palmer amaranth, a pigweed cousin, is one weed worth finding and removing now.
Palmer amaranth, a pigweed cousin, is one weed worth finding and removing now.

OK, I thought, big deal. It's in the Deep South. Man was I wrong! Now it's here, confirmed in 17 Indiana counties, and it's exerting its influence.

Bill Johnson, Purdue University weed control specialist, believes the situation is serious enough for you to scout carefully and identify Palmer amaranth from other pigweeds, even waterhemp. If you find it, report it and take action to get rid of it.

Here's the tips Johnson provides for identifying this weed and distinguishing it from its relatives in the pigweed family.

- The plant has no hair. Some other relatives do.

- Leaves are wide and ovate to diamond shaped

- Petioles, stem-like structures that connect the leaf blade to the main stem, are as long or longer than the leaf blade itself.

- The apical meristem in the center of the plant grows to capture as much light as possible, giving it a rosette-like appearance when looking directly down on the plant from above.

- Females have a long main terminal seed head that can reach up to 3 feet long. You read that right – three feet!

If you see this 'most wanted' weed, call Johnson at 765-494-4656 or email wgj@purdue.edu. You may also call his associate, Travis Legleiter, at 765, 496-2121, tlegleit@purdue.edu.