Palmer Amaranth
Amaranthus palmeri
Washington State Classification
Class A — Eradication Required Statewide
Palmer amaranth easily invades crop fields, especially annual crops.
Quick Reference
Identification
Growth Habit
An herbaceous, summer annual, Palmer amaranth can grow up to 10 feet tall, but usually 6-8 feet tall when it is not mowed. Can grow over 2 inches a day, in the right conditions.
Leaves
Leaves are egg-shaped to oval, with a small spine at the very tip of the leaf. They grow alternately up the stem, are hairless, and have white veins on the underside. The petiole, the stem that attaches the leaf to the main stalk, is longer than the leaf. Many Southwestern native tribes eat the leaves after cooking them.
Flowers
Plants are dioecious, either male or female. Both make green flowering spikes that age to brown.
Fruit & Seeds
Very small, round to oval, brown to maroon seeds. Female plants can make up to half a million seeds in a season. Seed can remain viable in the soil for up to 5 years. Many Southwestern native tribes eat the seed as a grain.
Impact
Palmer amaranth easily invades crop fields, especially annual crops. It can greatly reduce yield in those fields, and presence of its very small seeds in produce can prohibit that lot from being sold in many states. It is a prolific seed producer, very fast grower, and has many herbicide resistances.
Ecology & Spread
Habitat
Open, sunny areas, such as fields, cropland, rangeland, grassland, roadsides, and disturbed sites. Very drought tolerant.
Spread Mechanisms
Reproduction
Is a very prolific seed producer, which have a very high germination rate, and can stay viable in the soil for up to 5 years.
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