Amaranthus retroflexus

Species category

Weed

Common name

redroot amaranth

Diagnostic characters

Planting unit

True seedTrue seed:
A mature fertilized ovule consisting of an embryo, with or without and external food reserve (e.g., endosperm) enclosed by the testa.

Shape

LenticularLenticular:
Lens-shaped, circular in outline with convex sides.
and ovateOvate:
Egg-shaped with basal end the broadest.

Size

  • Length: 1.1–1.3 mm
  • Width: 1–1.1 mm
  • Thickness: 0.4–0.5 mm

Color

Black

Texture

Smooth and shiny

Other structures

HilumHilum:
The scar on the seed coat at the place of its detachment from the seed stalk (funiculus).
on basalBasal:
The base of the fruit or seed opposite the apical end.
end of margin.

Identification notes

EmbryoEmbryo:
A rudimentary plant contained in a seed, usually consisting of a more or less differentiated axis and attached cotyledon(s).
detectable on entire margin.

Noxious weed seed categories

State Noxious Weed: Arizona, Georgia, Indiana

AOSA examination list

Not included

More information

For more information, see ISMA fact sheet, Amaranthus spp.

Nomenclature

Family

Amaranthaceae

Valid name

Amaranthus retroflexus L.

Synonyms

Amaranthus retroflexus L. var. salicifolius I.M. Johnst.

 Amaranthus retroflexus.  Seeds with a detectable embryo on the margin.
Amaranthus retroflexus. Seeds with a detectable embryo on the margin.
 Amaranthus retroflexus.  Face view of seed. Hilum in notch. Photo courtesy of USDA-APHIS-PPQ.
Amaranthus retroflexus. Face view of seed. Hilum in notch. Photo courtesy of USDA-APHIS-PPQ.
 Amaranthus retroflexus . Close-up view of hilum. Photo courtesy of USDA-APHIS-PPQ.
Amaranthus retroflexus. Close-up view of hilum. Photo courtesy of USDA-APHIS-PPQ.