Palmer amaranth USDA PLANTS Symbol: AMPA
U.S. Nativity:
Habit: Forbs/Herbs
Amaranthus palmeri S. Wats.
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Taxonomic Rank: Magnoliopsida: Caryophyllales: Amaranthaceae
Synonym(s): carelessweed, Palmer amaranth, Palmer's amaranth
Appearance
Amaranthus palmeri is native to to the desert regions of the southwest United States and northern Mexico. It has become one of the most widespread, troublesome, and economically damaging agronomic weeds in the southeastern U.S. A. palmeri is an erect, branching, summer annual that usually grows from 6-8 ft (1.8-2.4 m) tall.
Foliage
The petiole is longer than the leaf. Petiole length is a key identifying characteristic. The alternate leaves are ovate to diamond shaped and some leaves will have a white watermark shaped like a chevron or V.
Flowers
Male and female flowers are borne on separate plants, and the small inconspicuous flowers are clustered tightly in linear or sparingly branched terminal spikes up to 18 in (45.7 cm) long.
Fruit
The seeds are shiny and dark reddish brown to brown. They are about 0.04-0.05 in (1-1.2 mm) in diameter.
Ecological Threat
A. palmeri thrives in hot weather, is tolerate of drought, and responds quickly to high levels of available nutrients. It competes aggressively against warm season crops, and is a prolific seed producer. A. palmeri populations have developed resistance to multiple herbicide modes of action, including ALS inhibitors, triazines, HPPD inhibitors, dinitroanilines, and glyphosate. This plant can have a greatly extended emergence period. Due to this extended emergence period producers must spend additional time and money to manage it.
Selected Images from Invasive.orgView All Images at Invasive.org


Flower(s);
Joseph LaForest, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage
Plant(s);
Rebekah D. Wallace, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage
Flower(s);
Rebekah D. Wallace, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage
Foliage;
Rebekah D. Wallace, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Bruce Ackley, The Ohio State University, Bugwood.org
Additional Resolutions & Image Usage
Stem(s);
Bruce Ackley, The Ohio State University, Bugwood.org
Additional Resolutions & Image Usage
Seedling(s);
John D. Byrd, Mississippi State University, Bugwood.org
Additional Resolutions & Image Usage
Flower(s);
Rebekah D. Wallace, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Joseph LaForest, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage
Fruit(s);
Joseph LaForest, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage
Plant(s);
Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org
Additional Resolutions & Image Usage
Seed(s); Seeds. Hilum in notch.
D. Walters and C. Southwick, USDA, Bugwood.org
Additional Resolutions & Image Usage
EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org 		 


State List
This map identifies those states that list this species on their invasive species list or law.

Invasive Listing Sources: