Amaranthus hybridus

Scientific Name Amaranthus hybridus L.
Synonyms Amaranthus chlorostachys (Willd.); Amaranthus incurvatus (Tim. ex Gren. & Godr.); Amaranthus patulus (Bertol.)
Common Names English: Slender Pigweed, Green Amaranth, Smooth Amaranth, Smooth Pigweed, Red Amaranth, Slim Amaranth; German: Bastard-Amarant; Spanish: Amaranto hibrido; French: Amarante hybride; Italian: Amaranto a spiga verde; Portuguese: Bredo
Description Glabrous or glabrescent annual forb, up to 15-100 cm (5.90 - 39.37 inch).


Characteristic Features

The floral bracts of A. hybridus are about 3-4 mm (0.12 - 0.16 inch), while the floral bracts of A. retroflexus are about 4-6 mm (0.16 - 0.23 inch) long. The sepals of A. hybridus usually have pointed tips, while the sepals of A. retroflexus have tips that are more flattened.

Young Plant

Cotyledons elliptical, with rounded tip, more or less petiolate. Seedlings with entire leaves, elliptical to ovate, with entire margin.


Elliptical, with rounded tip, more or less petiolate.


Central stem is light green or tan-green, round in circumference, ribbed, and usually hairy. Sometimes the lower portion of this stem is hairless.


Alternate leaves are up to 14 cm (5.51 inch) long and 7,5 cm (2.95 inch) across (excluding the petioles), becoming slightly smaller as they ascend the central stem. They are ovate or elliptic-ovate, smooth or slightly undulate along the margins, and pubescent or hairless. The lower side of each leaf has elevated pinnate veins. The uppermost leaves are smaller, lanceolate, and pubescent. This form of Slender Pigweed has predominately green foliage, although there may be red tints along the margins of the leaves and elsewhere. The petioles are quite long, causing the leaves to droop downward somewhat; they are often pubescent like the stems.

Propagation Organs


Staminate and pistillate flowers on the same plant, monoecious. Each type of flower has 5 cream sepals and no petals. The sepals are about 2 mm (0.078 inch) in length and oblong with short pointed tips. Each staminate flower (male) has 5 stamens, while each pistillate flower (female) has an ovary with 3 styles. Each type of flower is surrounded by several green bracts that are about 3-4 mm (0.12 - 0.16 inch) long and linear with long pointed tips.

Flowering Period

Summer-early fall.


Slightly wrinkled and dehiscent. The seed is contained in a bladder-like membrane (utricle). This utricle becomes tan and splits apart to release the seed.
Main germination is in spring.


The small seeds are flattened, dark brown or black, circular, and shiny.

Viability of Seeds

More than 10 years.


Spreads by reseeding itself. A single plant can produce over 100,000 seeds.



Weedy meadows, cropland, fallow fields, farm lots, vegetable gardens, gravelly areas along railroads, and waste areas. Highly disturbed and degraded habitats are preferred.


Loamy soil with high nitrogen content. The species is adaptable and can be found in gravelly soil, clay-loam, and moist to dry areas.

Additional Crop Information

Soybean, vegetables.

Agricultural Importance

Amaranthus hybridus is often confused with Amaranthus retroflexus (rough pigweed). A. hybridus is of world-wide distribution, being found in areas of South, Central, and North America, eastern Asia, Australia, and Africa. Due to its high reproductive output it is considered a problematic weed in agronomic crops. Multiple flushes of germination result in plants at different developmental stages. A. hybridus can cause yield reduction due to high weed densities. All pigweeds commonly hybridize.


Useful non-chemical contribution to Integrated Weed Management

A. hybridus can be suppressed by integrating cereals in the crop rotation.

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