What is Palmer amaranth?

Palmer amaranth (Amaranthus palmeri) is 

a problematic annual broadleaf weed in the 

amaranth genus. It has several common 

names including carelessweed, dioecious 

amaranth, Palmer’s amaranth, Palmer 

amaranth and Palmer’s pigweed. 

Palmer amaranth is native only to the 

Southwest and is considered a weed 

throughout the country. Field staff at the U.S. 

Department of Agriculture, Natural Resources 

Conservation Service, their partners, as 

well as farmers and landowners are working 

to eradicate these infestations before they 

spread to new areas.

Why the concern?

Palmer amaranth is a very fast growing 

weed that has spread out of native areas. 

Populations have developed resistance to 

multiple classes of herbicides with different 

modes of action, including glyphosate, 

making it very difficult and expensive to 

control, especially on productive farmland. It 

also is a highly competitive weed, and has 

been shown to be the most competitive of 

the pigweed species. Palmer amaranth has 

an extended germination and emergence 

window, rapid growth rates and high 

water use efficiency, and it produces large 

quantities of seed. It is a very prolific seed 

producer, producing up to 250,000 seeds 

from one plant. 

Palmer amaranth has a fast growth rate 

of approximately 2─3 inches per day and 

commonly reaches heights of 6─8 feet, 

greatly inhibiting productive crop growth. 

Yield losses have been reported up to 91% 

in corn and 79% in soybeans. The weed 

can also compete with and decrease other 

agricultural crop production.

Palmer amaranth can also be toxic to 

livestock animals due to the presence of 

nitrates in the leaves. 

What can you do?

As landowners and farmers, be proactive in 

identifying palmer amaranth on your property 

to prevent establishment. Familiarize yourself 

with the identification of this species, and 

actively search for it in your crop fields, 

borders, ditches, conservation lands and 

around dairies. 

If you suspect Palmer amaranth on your 

property, immediately call your local county 

extension agent and/or crop consultant to 

report it and get recommendations for control. 

Avoid entering areas where the plant is 

suspected or confirmed. If you must enter 

an infested area, always clean vehicles, 

equipment and clothing prior to exiting the 

area that has come in contact with the weed. 

Be certain machinery is clean when moved 

field to field.

Palmer 

Amaranth

Palmer 

Amaranth 

Key Points

• Palmer amaranth 

is a problematic 

annual broadleaf 

weed. 

• Palmer is native to 

the southwest U.S. 

but has spread 

across the country.

• Palmer has a fast 

growth rate of 

2─3 inches per 

day and commonly 

reaches heights 

of 6─8 feet. 

• Landowners and 

farmers can help by 

being proactive in 

identifying Palmer.

• Report any Palmer 

on your property 

to your local 

county extension 

agent and crop 

consultant.

Helping 

People 

Help the 

Land

Top banner photo: Palmer amaranth can be very 

prolific; one plant can produce up to 250,000 seeds 

(seeds shown above). Above: A male Palmer 

amaranth plant found in a farm field.
USDA is an equal opportunity provider, employer, and lender. USDA NRCS www.nrcs.usda.gov/ • April 2017

If planting grasses and flower mixes for 

conservation plantings, use only local 

reputable sources to ensure native plants are 

compatible with the area’s climate. Obtaining 

a seed laboratory report before purchasing a 

seed mix is recommended. Reject any seed 

lots which have “pigweed” or “amaranth” as 

a weed component unless the pigweed seed 

has been genetically tested to not be Palmer 

amaranth. Palmer amaranth seed is visually 

indistinguishable from other amaranth seed. 

Limit soil disturbance and utilize cover crops, 

like cereal rye, to prevent and help suppress 

weed infestations. Hay may also be planted 

to help provide protection against this weed. 

How do you identify Palmer 

amaranth? 

• Palmer amaranth is a summer annual that 

commonly reaches heights of 6─8 feet, but 

can reach 10 feet or more. 

• Green leaves are smooth and arranged 

in an alternative pattern that grows 

symmetrically around the stem. Leaves 

are oval to diamond-shaped. There is a 

small, sharp spine at the leaf tip. Some 

Palmer amaranth leaves have a whitish 

V-shaped mark on them. Not all plants 

display this characteristic. 

• There are separate male and female 

plants.

• Palmer amaranth looks similar to other 

pigweeds such as common waterhemp, 

redroot, and smooth pigweeds.

• Redroot and smooth pigweeds have fine 

hairs on their stems and leaves. Palmer 

amaranth and waterhemp do not have 

these hairs. 

• The stalk connecting a leaf to the stem of 

Palmer amaranth is longer than the length 

of the leaf. For common waterhemp, the 

stalk connecting a leaf to the stem will only 

be half the length of the leaf. 

• Seedhead spikes on female Palmer 

amaranth plants are much taller, up 

to 3 feet long, and more prickly than 

waterhemp, redroot and smooth pigweed 

spikes. Palmer flower heads 

are sharp and prickly to the touch with 

bare hands. 

A female Palmer amaranth plant found in a Dane 

County, Wis. farm field. Photo courtesy of University 

of Wisconsin─Extension.

Comparison of a Palmer amaranth petiole (the 

stalk that joins a leaf to a stem) length to the leaf 

blade length. Photo courtesy of University of 

Wisconsin─Extension.

Comparison of Palmer amaranth (left) to other similar 

species. Photo courtesy of University of Illinois.