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Palmer amaranth (Amaranthus palmeri) is an extremely competitive invasive weed that is highly adaptive. One plant can produce 100,000 to 500,000 seeds that may remain viable for 5 years. Under ideal conditions, amaranth can set seed as early as 4 weeks after germination. Older leaves differ from other amaranth species in that the petiole is as long as or longer than the leaf blade and the plant lacks hairs. Some populations have developed resistance to glypohosate and ALS herbicides; amaranth also has shown resistance to HPPD inhibitor and dinitroanaline herbicides in other areas.

Palmer amaranth foliage.

(Photo: Rebekah D. Wallace, University of Georgia, Bugwood.org)

Palmer amaranth stem.

(Photo: Bruce Ackley, The Ohio State University, Bugwood.org)

Management:

• Use herbicides before plants reach 4 inches in height.
• Use a combination approach of a pre- and post-planting herbicide.
• Note: Some populations may have developed resistance to certain herbicides.

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